Quercus ellipsoidalis

Northern pin oak [Blooms: Apr–May]

Male and female flowers of pin oakare spatially separated but often occur on the same branch. Female flowers have been reduced to only a short, green spike bearing three bright red styles; the female flowers emerge from leaf axils and may occur in clusters of up to three. The male flowers are borne on 1.5-4" long green catkins that dangle from bud clusters at the tip of the previous year's growth. The fruits are egg-shaped or elliptical (hence the species name) acorns 1/2-2/3" long with a deep reddish cap that covers about half the acorn.

Northern pin oak (Quercus ellipsoidalis) flowers and fruit. Bottom left: somewhat worn pin oak male catkins with some newly unfolded leaves. Top left: two female flowers on their pedicels, nestled in a leaf axil. Both flowers have three red styles but in each one of the styles is hidden by the angle of view. Top right: groups of pin oak female flowers nestled in two successive leaf axils. Note the variance of the length of the pedicels. In both leaf axils, a pair of flowers is present but the flowers further away are hidden by the closer blooms. Bottom right: a quartet of maturing pin oak acorns in mid-July.

In Northern pin oak, male and female flowers are spatially separated but often occur on the same branch. Female flowers have been reduced to just a short, green spike bearing three bright red styles; the female flowers emerge from leaf axils and may occur in clusters of up to three. The male flowers are borne on 1.5-4″ long green catkins that dangle from bud clusters at the tip of the previous year’s growth. The fruits are egg-shaped or elliptical (hence the species name) acorns 1/2-2/3″ long with a deep reddish cap that covers about half the acorn.

Northern pin oak (Quercus ellipsoidalis) is a tree native to the Great Lakes region and the upper Mississippi Valley that prefers dry, sandy soils. It can grow as tall as 60-70 feet tall and is fire-adapted. The bark on the trunk is dark brown to gray in color and deeply furrowed, with flat topped, blocky ridges in the bark. The bark of new twigs is often reddish brown and glossy. The leaves are green, glossy, 3-5" long and 2-4" across, and largely hairless, with 5-7 lobes separated by broad, rounded, deep sinuses; each lobe has 3-7 large, bristle-tipped secondary lobes with pointed tips. The underside of the leaves is dull and light green with patches of fine hairs where the lateral veins connect to the central vein. In the autumn, the leaves turn some shade of red (deep maroon to rusty red to scarlet). The leaves often remain attached to the tree through the winter, being shed with the opening of the new buds in the spring.

Northern pin oak (Quercus ellipsoidalis) leaves. (1) An early leaf that was emerging while the pin oak tree was in flower (May). The upper surface of the leaf is shown in (1a), the underside of the same leaf in (1b). (2) A mature leaf in July. The upper surface of the leaf is shown in (2a), the underside of the same leaf is shown in (2b). (3) The bark on the trunk of a northern pin oak tree; note the strong vertical furrows. (4) A mature leaf in situ. In both (2) and (4), note the broad, rounded sinuses and bristle-tipped lobes (the “pins” in the common name).

Northern pin oak is native to the Great Lakes region and the upper Mississippi Valley; it prefers dry, sandy soils. It can grow as tall as 60-70 feet tall and is fire-adapted. The bark on the trunk is dark brown to gray in color and deeply furrowed, with flat topped, blocky ridges in the bark. The bark of new twigs is often reddish brown and glossy. The leaves are green, glossy, 3-5″ long and 2-4″ across, and largely hairless, with 5-7 lobes separated by broad, rounded, deep sinuses; each lobe has 3-7 large, bristle-tipped secondary lobes with pointed tips. The underside of the leaves is dull and light green with patches of fine hairs where the lateral veins connect to the central vein. In the autumn, the leaves turn some shade of red (deep maroon to rusty red to scarlet). The leaves often remain attached to the tree through the winter, being shed with the opening of the new buds in the spring.

Northern pin oak (Quercus ellipsoidalis) is a tree native to the Great Lakes region and the upper Mississippi Valley that prefers dry, sandy soils. It can grow as tall as 60-70 feet tall and is fire-adapted. The bark on the trunk is dark brown to gray in color and deeply furrowed, with flat topped, blocky ridges in the bark. The bark of new twigs is often reddish brown and glossy. The leaves are green, glossy, 3-5" long and 2-4" across, and largely hairless, with 5-7 lobes separated by broad, rounded, deep sinuses; each lobe has 3-7 large, bristle-tipped secondary lobes with pointed tips. The underside of the leaves is dull and light green with patches of fine hairs where the lateral veins connect to the central vein. In the autumn, the leaves turn some shade of red (deep maroon to rusty red to scarlet). The leaves often remain attached to the tree through the winter, being shed with the opening of the new buds in the spring. Male and female flowers are spatially separated but often occur on the same branch. Female flowers have been reduced to only a short, green spike bearing three bright red styles; the female flowers emerge from leaf axils and may occur in clusters of up to three. The male flowers are borne on 1.5-4" long green catkins that dangle from bud clusters at the tip of the previous year's growth. The fruits are egg-shaped or elliptical (hence the species name) acorns 1/2-2/3" long with a deep reddish cap that covers about half the acorn.

A northern pin oak (Quercus ellipsoidalis) on the western shore of Bobolink Meadow by East Lagoon. This photo was taken fairly in the spring (May) when the male catkins had begun to wane and the leaves were just emerging.

 

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In bur oaks, both male and female flowers are produced on the same tree, but they are widely separated; the flowers are wind pollinated. Male flowers are borne on drooping, yellowish-green catkins 2-5" long that hang from the tips of the previous year's twigs; individual male flowers consist of 5-20 stamens surrounded by a lobed calyx. Some sources (e.g., http://www.missouribotanicalgarden.org/plantfinder/PlantFinderDetails.aspx?taxonid=280704) assert that the female flowers of bur oak also occur on catkins, but this is incorrect. Instead, the female flowers occur alone or in groups of 2-3 that arise in the leaf axils of new leaves. Individual female flowers are about 3 mm (1/8") long; a short, reddish green stalk (a pistil) covered with appressed scales bears naked reddish-green or light green styles on its tip. The female flowers are wind pollinated. Both male and female flowers form after the leaves begin to unfurl; the male catkins precede the female flowers by one to several weeks. Fertilized female flowers produce one or two acorns; the acorns may be nearly sessile or hang from short (<1") stalks. Mature bur oak acorns are 1.5-2.5" long and the same across (including the caps) — they are the largest acorn of any oak. The caps (= cupules) cover at least half of the length of bur oak acorns, often so much that only a nubbin of the acorn is visible. The caps are covered with coarse scales that have an obvious keel and appear knobby; the marginal scales on the caps bear soft awns up to 8 mm (1/3") long that form a conspicuous fringe above the acorn — this is the "bur" that is referred to in the common name in analogy to the machine tool used for grinding. The acorns mature and germinate over a single summer; they do not need to be exposed to cold to germinate.

Quercus

Quercus macrocarpa

bur oak [Blooms: Apr–May]

Velvetleaf is a ubiquitous, graceless plant loved by few but with a long history. The stems can reach up to 7' tall and are covered with short hairs. Flowers develop singly on 1" stalks arising from a leaf axil. Each flower is 3/4" across; it has 5 light-green, lance-shaped sepals covered in fine hairs and shorter than the petals, 5 golden yellow petals widest at their tips, numerous stamens with golden-yellow anthers, and a single pistil with multiply-branched styles. Velvetleaf was deliberately introduced to North America (by Ben Franklin) sometime before 1754 as a fiber crop, but soon escaped cultivation; before the introduction of herbicides, it was a serious agricultural pest, especially in corn fields. Native to Asia.

Abutilon

Abutilon theophrasti

velvetleaf [Blooms: Jul-Sep]

The flowers of amur maple occur in oblong clusters circular in section about 1.5" long and 1" across on the tips of the branches; flower clusters don't appear until after the leaves have emerged. There are two kinds of flowers in each cluster, both yellowish white in color, about 1/8" across, both with five sepals and five petals (each 1.5-2 mm long); the petals' tips curve in over the central parts of the flower. One flower type is staminate with eight stamens (no ovary or style) within the ring of sepals and petals. The other flower type is "perfect" with both eight stamens tipped with light yellow anthers and with a distinct central style rising above the stamens that bears a split tip that curls back. Minnesota Wildflowers [https://www.minnesotawildflowers.info/tree/amur-maple] states that the style splits in two, but the amur maple present in Jackson Park has perfect flowers whose styles either split in two or split in three — both morphs are present in the same flower cluster. Fertilized perfect flowers produce a fruit that is a pair of winged seeds (samaras) joined seed-to-seed with the wings making an angle of less than 30° (much less than most maples). Initially green in color, the samaras develop reddish highlights before turning bright reddish pink in mid to late summer. When the fruit matures in early to mid-autumn, each samara is 1-1.5" long and turns light brown.

Acer

Acer ginnala

Amur maple [Blooms: Apr–May]

Boxelder is dioecious — trees either produce all male (staminate) or all female (pistillate) flowers. Neither male or female flowers have petals; both consist of drooping, hairy filaments that bear either 5 reddish-brown anthers (male) or a greenish-white, deeply-forked style (female). The flowers are wind pollinated. Boxelder wood is soft and brittle so broken branches are common, but the trees can live to be a century old.

Acer

Acer negundo

boxelder [Blooms: Apr-May]

Norway maple produces separate male and female flowers, either on different trees or on the same tree. Flowers are produced in umbels of 10-30 flowers 2-3" across, either as the leaves are just unfolding or slightly before. Individual flowers are about 6-8 mm across; each has five 1/8" long sepals, five ~1/2" long petals, both of which are greenish yellow, and a brownish central disc. Male (pistillate) flowers have eight fertile stamens; female flowers have a green pistil with a pair of basal wings and a pair of styles, all surrounded by eight sterile stamens. Pollination occurs primarily by insects (bees). Fertilized female flowers produce pairs of winged fruits (samaras) joined at the seeds with an angle between the samaras of slightly less than 180°. The mature fruits are 1.5-2.5" long and turn brown in the autumn.

Acer

Acer platanoides

Norway maple [Blooms: Apr]

Perfect flowers are rare in red maple; individual trees may produce all male flowers, all female flowers, or both male flowers and female flowers on the same tree. Male flowers occur on the previous year's twigs (before the leaves open) as dense clusters 3/4-1" across composed of 1/8" long sessile flowers surrounded by short bracts with hairy margins; each flower has five sepals and five petals (making up a red or sometimes yellow bell-shaped corolla), and 5-8 slender, projecting stamens two to three times longer than the sepals. The female flowers also occur on the previous year's twigs before the leaves open as dense (3/4-1" across) clusters of initially sessile flowers, but the pedicels of the flowers soon elongate (to 1/2-2") and the flowers begin to droop; each 1/8" long flower has five sepals and five petals (making up a red or sometimes yellow bell-shaped corolla), and a two celled, hairless ovary with a pair of robust, arching red styles in the center. The flowers are wind pollinated. Fertilized flowers are soon transformed into a pair of red, winged samaras (i.e, maple seeds) joined tip to tip at a 45-90° angle. At maturity, the samaras are each 3/4-1" long. Like silver maple, the seeds of red maple can germinate in the same year they form (i.e., they don't need to overwinter to sprout).

Acer

Acer rubrum

red maple [Blooms: Mar-Apr]

Silver maples may produce male flowers on separate trees from the female flowers or both male and female flowers may be produced by the same tree. Flowers emerge before the leaves. Staminate flowers occur in small (1/3" across) clusters on short, lateral spurs from the twigs. The staminate flowers are yellowish-green to red. Individual staminate florets consist of four sepals and 4-6 stamens; there are no petals. Pistillate florets also occur in small (1/3" across) clusters on short peduncles bordered by several scaly bractlets; the florets are greenish-yellow to red in color. Individual pistillate florets consist of four sepals and a pistil with a pair of styles; there are no petals. The female florets are wind pollinated. Fertilized pistillate florets produce a pair of conjoined winged fruits (samaras) at about 90° from each other; when mature, the samaras are light brown and 1.5-2.5" long, falling to the ground in early summer. Unlike most other maples, silver maples produce fruits (samaras) that can germinate in the spring of the year in which they are produced.

Acer

Acer saccharinum

silver maple [Blooms: Mar]

Sugar maple trees may produce male and female flowers on separate trees or may produce male and female flowers on the same tree, even on the same branch. Male flowers are produced in drooping umbels, with 3-4" long, hairy pedicels. Individual male flowers are about 1/8" long consisting of a yellowish-green calyx with five teeth and 6-8 stamens with yellow anthers (in young flowers) that extend well outside the boundary of the calyx; petals are absent. Female flowers are also produced in drooping umbels; they are 1-2" long (including the hairy pedicel), but the flower itself is only 1/8" long consisting of a yellowish-green calyx with five teeth, a two-celled ovary, and a divided style that extends beyond the margin of the calyx. Again, petals are absent. The female flowers are wind pollinated. Fertilized flowers produce pairs of winged fruit (samaras) each about 1" long, with the two fruits at a 60-90° angle to each other. The samaras mature over the fall and must be exposed to an extensive interval of sub-freezing temperatures during the winter in order to germinate.

Acer

Acer saccharum

sugar maple [Blooms: Apr–May]

Yarrow is a quite common plant in late spring, 1-2' tall. The stem is unbranched until just below the flat or dome-shaped flower mass (which can be 2-4" across). Individual flowers are ~1/4" across with 5 white to cream colored ray florets (rarely pink or rose), shallowly notched at the tips, and 10-20 cream to pale-yellowish disc florets. The most recognizable feature of yarrow is the finely-divided, feathery or fern-like leaves, permitting a confident ID even when the plant is not in bloom.

Achillea

Achillea millefolium

yarrow [Blooms: May-Jun]

American sweet flag is common on east bank of Columbia Basin and occurs patchily on east bank of East Lagoon. Nearly identical to the (introduced) Eurasian sweet flag (Acorus calamus). The former has 3-6 major veins running the length of the leaf while the latter has only a single vein; the two are difficult to distinguish. The inflorescence is cigar-shaped and covered with hundreds of tiny (sterile) flowers.

Acorus

Acorus americanus

American sweet-flag [Blooms: May-Jun]

Ohio buckeye flowers occur on a robust, hairy panicle 4-8" tall, usually located near the tips of the smaller branches. The upper flowers in the panicle are primarily male (produce stamens only) while the middle and lower flowers are mostly perfect (produce both pistils and stamens). Flowers are about 1" across, consisting of 4 greenish-yellow petals with rounded tips (sometimes with a reddish patch near their base), 7 white stamens with orange anthers that are longer than the petals (exerted), and (in perfect flowers) a single white style longer than the stamens.

Aesculus

Aesculus glabra

Ohio buckeye [Blooms: Apr/May–?]

Bottlebrush buckeye is a shrub that can be up to 12' high. Flower spikes are 10-30" long and visually very striking. Individual flowers are tubular, several inches long, with stamens that protrude to double the length of the corolla. Native to Alabama and Georgia; introduced to Illinois. Foliage and fruit very similar to the native Ohio buckeye (A. glabra), but the flowers are quite distinct. Both the nuts and leaves are highly poisonous.

Aesculus

Aesculus parviflora

bottlebrush buckeye [Blooms: Jul-Aug]

Slender false foxglove plants are 12-14" tall. The flowers of slender false foxglove arise from the leaf axils. Flower buds are bright white and spherical; flowers range from pink to purple, and globular, attached to the tip of an elegant flower stalk (pedicel) and calyx reminiscent of a medieval trumpet (a buisine). The petals have fine hairs along their margins; there are dark purple spots on the lower interior of the flower.

Agalinis

Agalinis tenuifolia

slender false foxglove [Blooms: Aug-Sep]

Blue giant hyssop plants are 2-3.5' tall and smell strikingly of anise. Flower spikes are short (<6"). The calyx of the flower is tubular and blue-violet in color; the corolla is ~3/8" long, blue-violet, with an upper and lower lip between which protrude 4 stamens with blue-violet anthers and a style with a cleft tip. Similar to purple giant hyssop (Agastache scrophulariifolia) but the latter lacks the anise scent, has green rather than purple calyxes on the flowers, and the underside of the leaves is green, not white. Illinois Wildflowers website says "rare in Illinois …. known to occur in only Menard county…." (the Illinois Natural History Service adds Coles county).

Agastache

Agastache foeniculum

blue giant hyssop [Blooms: Jul-Aug]

Yellow giant hyssop plants are 4-7' tall; the stems are square and conspicuously winged. Flower spikes are up to 8" long. The calyx of the flowers is tubular and green in color; the corolla is ~3/8" long, nominally yellow, with an upper and lower lip between which protrude 4 stamens with yellow anthers and a style with a cleft tip. When in bloom, yellow giant hyssop is easily distinguished from other giant hyssops by the yellow/cream flowers.

Agastache

Agastache nepetoides

yellow giant hyssop [Blooms: Jul-?]

Purple giant hyssop plants are up to 6' tall; the stems are square. Flower spikes are short (<6"). The calyx of flowers is tubular and green; the corolla is ~1/4" long, lavender to pink and occasionally white (the common form in Jackson Park), with an upper and lower lip between which protrude 4 stamens with pink anthers and a style with a cleft tip. Similar to blue giant hyssop (Agastache foeniculum) but the latter smells of anise, has purple rather than green calyxes on the flowers, and the underside of the leaves is white, not green.

Agastache

Agastache scrophulariifolia

purple giant hyssop [Blooms: Jul-Aug]

White snakeroot's stems are light green or tan, 1.5-3' tall. Flower clusters are 2-6" across with 9-25 flowers. Individual flowerheads are 1/2" across, composed of 10-30 disk florets with bright white, 5-lobed, spreading corollas and (extended) styles; ray florets are absent. The flowerheads are superficially similar to boneset (Eupatorium spp.) but very different in detail and the leaves of each are distinctive. White snakeroot blooms late into the fall. This plant is highly toxic. The toxins (collectively known as tremetol) are passed to the meat and (especially) milk of herbivores that eat the foliage. Snakeroot toxins (in milk from a dairy cow) likely caused the death of Abraham Lincoln's mother, Nancy Hanks Lincoln.

Ageratina

Ageratina altissima

white snakeroot [Blooms: Jul-Nov]

Swamp agrimony has flowers that are yellow and about 1/4" across; they have a tubular green calyx, five yellow petals, about 10 stamens, and a single pistil.

Agrimonia

Agrimonia parviflora

swamp agrimony [Blooms: Aug-?]

Hollyhock flowers are bowl-shaped and large (3-5" across) with a prominent stalk-like central structure that contains the stamens apically and styles basally. There are 5 petals, 5 sepals, and 6-9 sepal-like bracts; color can vary from white to deep purple.

Alcea

Alcea rosea

hollyhock [Blooms: Jul-?]

Water plantain is another plantain that's not a plantain, but it does look like one. This plant is an emergent aquatic with a basal rosette of large (up to 7"x 4"), hairless leaves with long petioles that are filled with distinctive spongy tissue (like a cellular foam); the leaves are (largely) parallel-veined. A tall (up to 3') highly-branched, whorled inflorescence rises from the center of the basal rosette; at the tip of each branch is a single 1/4" wide flower with three white petals (with a spot of yellow at their bases), three green sepals (with transparent margins) about half the length of the petals, and six stamens surrounding a greenish center that bears 1-2 dozen pistils. Water plantain is apparently popular with muskrats. Small-flowered water plantain (Alisma subcordatum) is more common in Illinois, but not known from Jackson Park; water plantain and small-flowered water plantain are nearly identical, but the latter has smaller flowers (1/8") and the petals and sepals on the flower are the same length.

Alisma

Alisma triviale

northern water-plantain [Blooms: Jun-Aug]

A short, sparsely-branched plant with alternate leaves. Flowers are clustered at the apex of the plant. Each 1/4"-3/8" wide flower has 4 white petals, 4 light green sepals, 6 stamens with yellow anthers and a stout, cylindrical style; the stigma is a flat disc. Garlic mustard's leaves are superficially similar to ground ivy (Glechoma hederacea), but less rounded; the flowers of each species are distinctive. A highly aggressive woodland invader introduced from Eurasia as an edible herb.

Alliaria

Alliaria petiolata

garlic mustard [Blooms: Apr-Jul]

Wild garlic's flower stalk holds a 1-2" wide inflorescence surrounded by 2-3 bracts; the bracts dry to a papery, off-white membrane tapering to a long point that contains flower buds on a pedicle, bulblets without pedicles, or both. When open, the flowers (~1/2" across) are each elevated on a 3/4" pedicle and exhibit six white, light pink or pink, sharply pointed tepals (= petals + sepals), six stamens, and a central light green ovary with a single style. Allium canadense is the most common Allium here; it can be distinguished from other native species by the presence of the aerial bulblets. The other common species in Jackson Park (nodding onion, Allium cernuum) is easily distinguished by the "nodding" of the entire inflorescence. (Neither of these is the "wild onion" Chicago is named for; that is Allium tricoccum.)

Allium

Allium canadense

wild garlic [Blooms: Jun-?]

Nodding onion's flower stalks are 12-18" tall, smooth, nearly vertical, and bend 180° at their tips (like a shepherd's crook); the ~2" wide flower cluster hangs below. Each of the 40-60 flowers hangs from a 1/2-1" hairless pedicel; each white, light pink, or light lavender flower has six tepals (three true petals and three similar-appearing sepals), six stamens (with yellow anthers) that extend well beyond the petals, and a single ovary with a style at least as long as the stamens. This is our only wild onion that "nods" so should be easy to identify. It's very popular with bees.

Allium

Allium cernuum

nodding onion [Blooms: Jul/Aug–?]

Black alder is monoecious and produces separate male (staminate) and female (pistillate) florets on the same tree, both partially formed in the season before they bloom and overwintering before they become fertile. Male catkins occur in clusters of 2-5 reddish-yellow catkins, each 2-3" long when mature, narrowly cylindrical, and drooping. Male florets occur in clusters of 3-6 along the catkins, partially hidden by oval, brown bractlets. Each male floret consists of a four-lobed calyx and four stamens; petals are absent. The female florets are produced in sparse, open, branched clusters of reddish cone-like catkins, each initially about 1/4" long but growing to 3/4-1" long and 1/2" across. Within each female cone, female florets occur in clusters of 2-3, partially hidden by bractlets. Each female floret consists of a naked ovary with a pair of tiny styles at its tip that are wind pollinated. After fertilization, the male catkins wither; the bractlets of the female catkins become brown and woody, producing a very pine-like cone with the seeds nestled beneath the bractlets. The egg-shaped, flattened seeds are formally samaras, but the wing is reduced to narrow ridges. The female cones can persist through the winter.

Alnus

Alnus glutinosa

black alder [Blooms: Mar-Apr]

The end of green/red amaranthus stem bears a bristly panicle of tiny flowers up to 18" tall; the flowers are either staminate (male) or pistillate (female), but both occur on each plant. The flowers are wind pollinated. Flowers lack petals but have five pink sepals 2 mm long with pointed tips (which, together with associated 3-4 mm long, red bracts, produce the bristly appearance). Male flowers have five stamens while female flowers have a single ovary with three stigmas.

Amaranthus

Amaranthus hybridus

green/red amaranth [Blooms: Sep-?]

At the apex of the stem of Palmer's amaranth is a panicle up to 18" long covered with tiny green flowers that are wind-pollinated. Flowers have 4-5 petals. Individual plants produce either staminate (male) or pistillate (female flowers) but not both; perfect flowers are unknown.

Amaranthus

Amaranthus palmeri

Palmer's amaranth [Blooms: Aug–?]

The tip of the stem of redroot amaranth produces a panicle of greenish-white flowers; smaller panicles of flowers also arise from the axils of the leaves in the upper half of the plant. Both male (staminate) and female (pistillate) flowers appear in the same inflorescence; perfect flowers are absent. Individual flowers lack petals but have 5 white tepals that are about 3 mm long and one or more small (3-6 mm) green, bracts under the flower whose midrib extends to form a spine; male flowers also have 3-5 yellow stamens, while female flowers also have an ovary with a 3-parted style on the top of the ovary.

Amaranthus

Amaranthus retroflexus

redroot amaranth [Blooms: Aug-Oct]

Common ragweed is a highly branched, weedy plant that gets about 3' tall. Numerous stems bear cylindrical flower spikes 1-6" long and 1/4" wide; the flowers are tiny (1/8"), all male (except near the base of the spike) in cup-like involucres that are initially green but turn yellowish-green with age, bead-like, hanging from short stalks. The actual male flowers are hidden in the involucre, lack petals, have numerous yellow anthers and (notoriously) produce copious yellow pollen that is carried by the wind; female flowers are enclosed in leafy bracts with protruding paired white styles, and occur in cryptic clusters on the stems below the flower spikes and in leaf axils. If you suffer from seasonal allergies, this plant and its cousin, giant ragweed, are the culprits, NOT the unfairly maligned goldenrod (which has sticky pollen that never gets airborne). Common ragweed has pinnatifid (pinnate-like) leaves; giant ragweed has deeply-lobed leaves that appear palmate.

Ambrosia

Ambrosia artemisiifolia

common ragweed [Blooms: Aug-?]

Male (staminate) and female (pistillate) flowers are physically separated on Western ragweed plants with the male flowers on spike-like racemes 1-6" long that arise from the upper stems, while female flowers occur more basally in small clusters at the base of the spike, along stems, or from leaf axils. Individual staminate flowerheads occur along the entire length of the spike, facing in all directions. They are 2-5 mm across, drooping from 1-4 mm long peduncles and developing a short, bell-like shape as they mature; they are covered by 3-5 oval, fuzzy phyllaries (bracts) in a single series where the lower half of each phyllary is fused to the other phyllaries. Beneath the phyllaries are approximately four staminate florets, each bearing five stamens with pale yellow anthers. The pistillate flowerheads are egg shaped and occur in clusters with a basal bract up to 1.25" long; pairs of smaller bracts lie just below each individual pistillate flowerhead. Pistillate flowerheads each sit in a cup of fused phyllaries 8 mm long and 3 mm across that has several tooth-like projections; each cup holds a single pistillate floret with a bifurcated style protruding from the apex of the floret. The florets are wind pollinated. Like other Ambrosia species in Jackson Park (common ragweed and giant ragweed), Western ragweed may contribute to hay fever symptoms. Western and common ragweed are similar to each other, but Western ragweed (almost always) has simple-pinnate leaves while common ragweed has double-pinnate leaves that are more deeply lobed and fern-like; Western ragweed is the hairier of the two.

Ambrosia

Ambrosia psilostachya

Western ragweed [Blooms: ?-Nov]

Giant ragweed is a much larger (up to 12' tall) cousin of common ragweed (A. artemisiifolia) but similarly bushy and weedy, with a candelabra-like appearance in the upper parts of the plant. The upper stems bear 3-6" long flower spikes, all male (except near the base of the spike) in 1/8" wide cup-like involucres that are initially green but turn yellowish-green with age, hanging from short stalks. The actual male flowers are hidden in the involucre, lack petals, have numerous yellow anthers and (notoriously) produce copious yellow pollen that is carried by the wind; female flowers are enclosed in leafy bracts with protruding paired white styles, and occur in cryptic clusters on the stems below the flower spikes and in leaf axils. If you suffer from seasonal allergies, this plant and its cousin, common ragweed, are the culprits, NOT the unfairly maligned goldenrod (which has sticky pollen that never gets airborne). Common ragweed has pinnatifid (pinnate-like) leaves; giant ragweed has deeply-lobed leaves that appear palmate.

Ambrosia

Ambrosia trifida

great ragweed [Blooms: Aug-Sep]

Downy serviceberry is a shrub or small tree 10-30' tall that blooms very early in the spring, before (most) leaf emergence; this is the most common Amelanchier sp. in Illinois. Downy serviceberry flowers bloom in a cluster of 5-12 before or early in leaf emergence. (Emerging leaves are folded and bronze-tinged.) Flowers are 1" across with a short, light green, a hairy calyx with five narrow triangular teeth 1/3 the length of the petals that are strongly bent back towards the stem; five narrow, oblong white petals; 15-20 stamens with creamy yellow anthers; a hairless green ovary; and a green pistil with a single five-parted style. Downy serviceberry flowers can be easily distinguished from Wiegand's shadbush (Amelanchier interior); the former has a hairless ovary while the latter has an ovary whose top is densely covered with wooly hairs. The very hairy undersides of downy serviceberry leaves are also a good clue to its identity, although other Amelanchier spp. also have (less) hairy leaves.

Amelanchier

Amelanchier arborea

downy serviceberry [Blooms: Apr-May]

Wiegand's shadbush (aka, serviceberry) is a shrub or small tree up to 10m tall, uncommon in Illinois and restricted to the northeastern portion of the state. The flowers bloom in clusters of 6-12 simultaneously with leaf emergence. (Emerging leaves are folded and bronze-tinged.) The flowers are 1" across with a short, light green, hairy calyx with five narrow triangular teeth 1/3 the length of the petals, strongly bent back towards the stem; five narrow, oblong white petals; 18-20 stamens with creamy yellow anthers; a characteristic green ovary densely hairy on the top; and a green pistil with a single five-parted style. Wiegand's shadbush flowers can be easily distinguished from downy serviceberry (A. arborea); the former has an ovary whose top is densely covered with wooly hairs while the latter has a hairless ovary.

Amelanchier

Amelanchier interior

Wiegand's shadbush [Blooms: Apr-May]

Marram grass forms a culm that remains short (~2") if no inflorescence is produced but reaches heights of 30" with an inflorescence. Culms produce a 6-12" long spike-like panicles of single-flowered spikelets each 9-15 mm long. Flowers are wind-pollinated, as is common in grasses. This plant is endangered in Illinois and is restricted to beaches along the Lake Michigan shoreline where it is often the dominant grass.

Ammophila

Ammophila breviligulata

marram grass [Blooms: Jul-?]

Lead plant is a sprawling bush 1-3' tall. the stems, leaves, flower spikes, and flower calyxes are densely covered with white, wooly hairs (giving the appearance of a metallic surface). The flower spikes are up to 6" long; they arise from the ends of branches. Flowers are 1/4" long, purple with reddish stamens and golden anthers; there is a single petal on the upper side of the flower that is initially tubular but opens after pollination to nearly flat (horizontal). Lead plant is considered an indicator of high-quality habitat; its tap roots can reach up to 5 m long. The flowers of lead plant look like false indigo (Amorpha fruticosa), but the latter is a much larger shrub.

Amorpha

Amorpha canescens

lead plant [Blooms: Jun-Sep]

Sharp-lobed hepatica is an early-blooming, woodland wildflower with distinctive 3-lobed, superficially palmate, variegated basal leaves on long petioles. The flowers are 1" across, borne on naked, reddish, hairy stalks ~4" long. Flowers consists of 5-11 (typically 6) blue, white, or lavender, oblong petals (actually, sepals), copious white stamens, and numerous green carpels; behind the flower are 3 reddish, hairy bracts shorter than the petals. The fruits are hairy, elliptical achenes with a short, pointed, brittle beak. all cupped in the center of the bracts that lay behind the flower. ITIS considers Hepatica acutiloba a junior synonym of Anemone acutiloba; the USDA Plants Database, IUCN Red List, and NatureServe Explorer considers H. acutiloba as a junior synonym of Hepatica nobilis. All agree it is "sharplobed hepatica." The roundlobed hepatica (which is either a variety of sharplobed hepatica or a separate species, depending on which authority you prefer) is identical except that the lobes on the leaves are smoothly rounded.

Anemone

Anemone acutiloba

sharp-lobed hepatica [Blooms: Apr]

The petals (actually, sepals) of Canada anemone flowers are rounded; the pistillate cone in the center of the flower is approximately hemispherical and less than 10% of the flower width. The fruit is a round cluster of flattened seeds. The five-lobed leaves of Canada anemone are superficially similar to those of wild geranium (Geranium maculatum) but are sessile, not borne on petioles. Canada anemone is the commonest flower in Jackson Park in the late spring and summer.

Anemone

Anemone canadensis

Canada anemone [Blooms: May–Sept]

Thmbleweed flowers are borne on long (1-2') stalks; each flower is about 3/4" across with 5 pointed white petals-like sepals that often remain partially closed; the green pistillate cone in the center of the flower is about twice as long as it is wide (i.e., a tall gumdrop) ~20% of the flower diameter. A. canadensis may also have pointed petals, but the cone in the center of the flower is hemispherical (a short gumdrop). Thimbleweed (A. cylindrica) is best distinguished from tall anemone (A. virginiana) by the shape of the leaflets — A. cylindrica has leaflets with a wedge-shaped base with the lobes radiating out from the base, while A. virginiana has a rounded leaflet base with toothed distal margins.

Anemone

Anemone cylindrica

thimbleweed [Blooms: Jun-Jul]

Wood anemone produces slender green, hairy stems that bear either alternate leaves or (more typically) a whorl of three compound leaves at the apex of the stem; the 5 cm tall flower stalk arises from the center of the whorl. The flower stalks each bear a single white (sometimes pink) flower 1" across with 4-9 petal-like sepals and 30-60 stamens with white anthers surrounding numerous simple pistils.

Anemone

Anemone quinquefolia

wood anemone [Blooms: Apr–May]

Tall anemones have leaves on long petioles (like A. cylindrica). The petals (actually, sepals) of the flowers are pointed (like A. cylindrica); the pistillate cone in the center of the flower is approximately hemispherical and >1/3" across, about 20% of flower diameter. Thimbleweed (A. cylindrica) is best distinguished from tall anemone (A. virginiana) by the shape of the leaflets — A. cylindrica has leaflets with a wedge-shaped base with the lobes radiating out from the base while A. virginiana has a rounded leaflet base with toothed distal margins.

Anemone

Anemone virginiana

tall anemone [Blooms: Jun–Jul]

Field pussytoes flowerheads are either pistillate (female) or staminate (male), both about 8 mm long, both looking like a compact tuft of white hairs. The very similar plantain-leafed pussytoes (A. plantaginifolia) looks much the same but has basal leaves with three main veins (best viewed from the underside) rather than one.

Antennaria

Antennaria neglecta

field pussytoes [Blooms: Apr-May]

Male and female flowers of Parlin's pussytoes occur on separate plants as clusters of 4-12+ flowerheads on a stalk; colonies of male plants are often well separated from colonies of female plants. (Colonies form from extensive, horizontal stolons that arch upward at their tips.) Female flowerheads are 1/3-3/4" long and look like miniature shaving brushes — the reddish or purple-tinged thread-like styles protrude from the top of the flowerhead. Each flowerhead is surrounded by bracts (phyllaries) that are green and leaf-like at their base, thinning to a translucent white, petal-like tip. Individual florets are 4-7 mm long (up to about 1/4"); the phyllaries are 7-13 mm long (up to 1/2"). Male flowerheads are less furry than the female flowerheads, consisting of scaly, white male florets 3.5-5 mm long with a brown column of stamens protruding from the center of each floret. The phyllaries on the male flowerheads are 6-9 mm long. The fruits are 1-2 mm long brown seeds with a tuft of 5-8 mm long white hairs to help loft them into the wind. Parlin's pussytoes is one of the host plants for the larvae of the American painted lady butterfly (Vanessa virginiensis). Some reproductively isolated populations (2N chromosome numbers of 56, 70, 84, and 112 all exist in the wild) apparently lack male plants altogether and reproduce by gynoecy (like several cultivated vegetables). Missouri Wildflowers seems to deny that A. plantaginifolia is a distinct species from A. parlinii, but both Antennaria plantaginifolia and Antennaria parlinii are recognized by ITIS.gov and the USDA Plants database. Note that both Parlin's pussytoes and plantain-leafed pussytoes have at least three veins on the basal leaves so may be easily confused in the field. The basal leaves of plantain-leafed pussytoes are often hairier than those of Parlin's pussytoes, which are thus greener, but the best way to distinguish the two species is by the larger size of the flowers and seeds of Parlin's pussytoes.

Antennaria

Antennaria parlinii

Parlin's pussytoes [Blooms: Apr]

Plantain-leafed pussytoes is a short (6" tall) plant. The basal leaves are 2" wide and 3.5" long, spoon-shaped with long petioles, grayish green, with 3-5 conspicuous main veins; the lower surface is densely covered with appressed hairs and is shiny white. Individual plantain-leafed pussytoe plants bear either male or female flowers exclusively. Flowerheads are short (<1/2" long) and composed exclusively of white disc florets surrounded by a layer of phyllaries; female florets are fluffy white from the profusion of styles (looking a bit like Q-Tips) while male florets show tubular, brownish anthers. Asexual reproduction may produce colonies of exclusively male or female plants. The similar field pussytoes has basal leaves with only a single (rather than 3-5) main veins.

Antennaria

Antennaria plantaginifolia

plaintain-leafed pussytoes [Blooms: Apr-May]

The main stems and some of the lateral branches of dogbane produce panicles of flowers 1-3" across on their tips; the central flowers in the cluster open first. Individual flowers are tiny — 2-3 mm across and 3-5 mm long, bell-shaped, with a fluted edge produced by the 5 white pointed petals. The stamens are shorter than the petals and curve toward the center of the flower, forming a cone over the ovoid stigma.

Apocynum

Apocynum cannabinum

common dogbane [Blooms: Jun-Aug]

Spectacular and unmistakable red and yellow, columbine's bell-like flowers hang aperture down from an arching flower stalk; the four elongate, parallel spurs point up while the stamens and style emerge from the bottom of the flower. This is the only columbine native to Illinois.

Aquilegia

Aquilegia canadensis

red columbine [Blooms: Apr-Jun]

An ornate pink flower with multiple levels of petals above a central core of projecting yellow stamens. This variant of Aquilegia vulgaris ("stellata" commercially called 'Nora Barlow') is a genetic variant that produces multiple stacked flowers (like the difference between a wild rose and commercial roses).

Aquilegia

Aquilegia vulgaris

common columbine [Blooms:May-Jun]

Japanese angelica tree may be mistaken for the (native) devil's walking stick, Aralia spinosa. However, the Japanese angelica tree (A. elata) has shorter (although quite substantial) compound leaves, sessile leaflets directly attached to the petiolule, a smaller inflorescence (about 2' tall rather than over 3'), and shorter, less intimidating spines on the trunk. Leaf venation (best viewed from the underside) is the best way to differentiate the two. In devil's walking stick, the pinnate leaf vein tips curve to form a sub-marginal vein parallel to the leaf margin. In the Japanese angelica tree, the leaf veins extend all the way to the margins of the leaf.

Aralia

Aralia elata

Japanese angelica tree [Blooms: Jul/Aug–?]

Spikenard is superficially similar to devil's walking stick (Aralia spinosa) but lacks the spiny leaves and stem of the latter. Both produce a terminal inflorescence of flowers (20+ ft. up). Unlike devil's walking stick, the flowers of spikenard are perfect; i.e., they have both male (stamens) and female (a stigma) parts. In this photo, both flower buds and flowers with prominent stamens are apparent.

Aralia

Aralia racemosa

spikenard [Blooms: Jul-Aug]

A small, somewhat shrubby tree up to 25' tall, although half that height is more common in Jackson Park (which is near the northern limit of its range). Devil's walking stick produces a terminal inflorescence of flowers (20+ ft. up). Flowers are small (1/4" long), white and are produced in umbels at the top of the tree. Devil's walking stick has flowers that are either male (bearing stamens) or female (bearing styles). The male flowers of devil's walking stick have prominent stamens and five white, triangular petals; the female flowers (shown here) look like rounded green buds with five stout styles emerging from the distal end.

Aralia

Aralia spinosa

devil's walking stick [Blooms: Aug-Sep]

Burdock has thistle-like, composite flowers with lavender to purple (rarely, white) disc florets but no ray florets; the surrounding bracts are green and strongly hooked.

Arctium

Arctium minus

burdock [Blooms: Jul-Oct]

Bearberry produces small clusters of 2-15 flowers from the tips of the previous year's twigs. Individual flowers are urn- or bell-shaped with a constricted opening ringed by five short lobes, 1/2" long and wide; they have a five-lobed flattened calyx, a white or pink corolla, 10 stamens, and a single style none of which protrude outside the corolla. The flower pedicels are about 1/4" long, red and have a narrow bract at their base. The fruit is a spherical drupe 1/4-1/2" across, initially whitish green but red at maturity.

Arctostaphylos

Arctostaphylos uva-ursi

bearberry [Blooms: April]

Two thyme-leaved sandwort flowers, with leaves clearly visible on the stem on the left of the image. Easily overlooked as just another chickweed, thyme-leafed sandwort's petals are not deeply notched like chickweeds. The stems are 6-10" tall, erect or sprawling, dark purple, and covered with fine hairs. Tiny (4 mm) white flowers on 1/4" pedicels with backward-pointing hairs; flowers have five pointed, white, oblong petals; five hairy green sepals longer than the petals; ten white stamens with magenta anthers; a green central ovary; and three white styles. An exotic from Europe that prefers disturbed areas with minimal other vegetation.

Arenaria

Arenaria serpyllifolia

thyme-leaved sandwort [Blooms: Apr-Jun]

Jack-in-the-pulpit is iconic and unmistakable wildflower. Plants are 1-2' tall; they don't flower until at least 3 years old. Each plant has a single upright stalk (a.k.a., the peduncle) that produces the inflorescence; the stalk develops directly from an underground storage organ, the corm. The inflorescences are light green to reddish green, often with reddish-brown stripes. The outermost spathe wraps loosely around the robust, cylindrical spadix; the top of the spathe bends 90° to form a hood (the "pulpit") over the spadix ("Jack"). The top half of the spadix produces volatile compounds that attract small insects, especially fungus gnats; the insects carry the pollen between plants. The bottom half of the spadix bears highly reduced florets. Both male and female florets lack petals; male florets consist of four stamens while female florets consist only of a stigma attached directly to the top of the ovary. Each plant typically has EITHER male or female florets located on the bottom half of the spadix; a single plant usually produces only one sex of florets in a given season, but plants switch between male and female multiple times during their ~20 year lifespan (they are "sequential hermaphrodites").

Arisaema

Arisaema triphyllum

Jack-in-the-pulpit [Blooms: Apr-Jun]

Flowerheads of pale Indian plantain. These plants can be to 9' tall and commonly reach 6+ feet; the stem is pale green to purple with a whitish cast. The flat-topped apical flowerhead is shaped like an inverted pyramid made up of small (1/8x3/8") tubular, cream-colored flowers with five disc florets surrounded by five bracts.

Arnoglossum

Arnoglossum atriplicifolium

pale Indian-plantain [Blooms: Jun-Aug]

Prairie Indian plantain flowerheads are tubular, 3/16" x 3/8", greenish white to reddish white, with five disc florets surrounded by five bracts with white keels (which distinguishes them from pale Indian plantain flowerheads).

Arnoglossum

Arnoglossum plantagineum

prairie Indian-plantain [Blooms: Jun-Jul]

Red chokeberry is a 6-12" tall shrub with multiple stems. Flowers are white with red tinge on the tips of the 5 petals; each flower is ~1" in diameter.

Aronia

Aronia arbutifolia

red chokeberry [Blooms: Apr-May]

Black chokeberry flowers occur in clusters of 7-12 near the margins of the shrub. Each flower is ~1/2" across with a reddish-green calyx with 5 short triangular lobes, 5 white, spoon-shaped, non-overlapping petals with rounded tips and a narrow base, 16-20 stamens with pink to rose-colored anthers, and 5 pale green styles, fused at their bases. The red glands on the upper leaf midvein and pink to rose-colored stamens are diagnostic of black chokeberry.

Aronia

Aronia melanocarpa

black chokeberry [Blooms: May-?]

Beach wormwood is an unusual plant 2-4' tall with characteristic, deeply dissected leaves. The flowerheads are 2-4 mm long and wide; each is composed of 5-20 outer disk florets that bear only stamens and 8-30 inner disc florets that possess both pistils and stamens. There are no ray florets.

Artemisia

Artemisia campestris

beach wormwood [Blooms: Aug-Sep]

Mugwort's Inflorescence consists of leafy spikes covered with inconspicuous flowerheads, initially whitish-green, later yellowish- or purplish-green; the flowerheads are egg-shaped, very small (1/8" across) and bear only disc florets (ray florets absent).

Artemisia

Artemisia vulgaris

mugwort [Blooms: Jul-Oct]

Wild ginger's flowers are ~1-2" across, reddish-brown on the outside, cream colored on the inside, that develop from an axis at the junction of the two leaves (one flower per plant). The flower calyx consists of three triangular sepals with the long tips curled backwards; the tubular base of the calyx is divided into three pairs of chambers (six total) which contain the ovaries, twelve stamens, and six reddish-brown styles. Because the flowers are brown and occur right at ground level, they are easy to overlook and usually can only be seen by parting the leaves.

Asarum

Asarum canadense

wild ginger [Blooms: Apr/May-?]

Prairie milkweed produces one and a half to two inch balls of 30-100 greenish-white flowers in the axils of a few of the mid-stem and upper leaves; the flowers are supported on 1/2"-3/4" pedicels. Each flower is about 1/8" across and 1/4" long; the flowers are a variation on the typical (complex) milkweed morphology with 5 sepals, a 5-lobed corolla with 5 petals (often with purple blotches at their tips) that are reflected backwards to cover the top of the pedicel, 5 hoods without horns, and a short central column that rises above the hoods; there is a distinct gap between the bases of the petals and the crown. Seedpods are 4-5" long with a fat base (attached to the pedicel) tapering rapidly to a narrow tip. Prairie milkweed can be confused with whorled milkweed (Asclepias verticillata) — both occur in Jackson Park — but whorled milkweed has even narrower (grass-like) leaves than prairie milkweed, is a shorter plant, and has pure white flower that do bear horns.

Asclepias

Asclepias hirtella

prairie milkweed [Blooms: Jun-Aug]

The flowerheads of swamp milkweed are erect, ~3" across, with 10-40 flowers; flowers are 1/4" across and typical milkweed morphology with pink petals and whitish hoods, but color can vary from pink to magenta; the central column is cream-colored and visible below the base of the hoods. The petals are reflected backwards but are not tightly pressed against the stem; the horns arch up and over the central column and taper to a sharp point.

Asclepias

Asclepias incarnata

swamp milkweed [Blooms: Jul-Aug]

The height of the stem and the leaves of Sullivant's milkweed are similar to common milkweed. Each plant produces 1-3 (total) flower clusters from the stem apex and adjacent leaf axils; each cluster is 2-4" across and has ~15-25 flowers, each ~1/2" across. The flower petals are pink to rich purple, with white bases; the hoods are usually noticeably lighter. The horns are laterally compressed (sickle-shaped) and their tips clearly overlap over the column.

Asclepias

Asclepias sullivantii

Sullivant's milkweed [Blooms: Jul-Aug]

Common milkweed's flowers arise from leaf axils, are 2.5-5" wide, hemispherical, and covered with typical 1/2" wide milkweed flowers ranging from light pink to reddish-purple; the petals, reflexed back around the base of the flower are darker than the hoods.

Asclepias

Asclepias syriaca

common milkweed [Blooms: Jun-Aug]

Butterfly weed has clusters of 8-25 flowers, in various shades of orange with touches of yellow or red, that arise from the stems and leaf axils. Individual flowers have a typical milkweed morphology, with the petals reflexed backwards over the flower stalk and the complex corona protruding. The central column of the corona in A. tuberosa is always yellow regardless of the shade of the remainder of the flower. This is the only Illinois milkweed with orange flowers and has narrower leaves than all other local milkweeds except whorled milkweed (A. verticillata, which has white flowers).

Asclepias

Asclepias tuberosa

butterfly milkweed [Blooms: Jun-Sep]

Whorled milkweed's flowers are white, occurring in small (1-3") clusters that rise from leaf axils. Individual flowers are typical milkweeds (except for their color), 1/4" across; horns are sickle-shaped, petals are white or greenish-white. Once you recognize that this plant IS a milkweed, given its grass-like leaves in whorls, it is impossible to mistake it for any other local species.

Asclepias

Asclepias verticillata

whorled milkweed [Blooms: Jul-Sep]

Canada milkvetch flower stalks are ~6" long, covered by numerous (up to 75) cream-colored, tubular flowers (right side of image). Individual flowers are 1/2-3/4" long, slightly drooping, with five petals making up the tube (like an elongated pea flower) and a short (~1/4") cylindrical calyx of the same color with five thin, green teeth; the tip of the upper petal is reflected upwards. The fruits (left side of image) are short, pea-like legumes packed tightly along the flower spike.

Astragalus

Astragalus canadensis

Canada milkvetch [Blooms: Jun-Aug]

White wild indigo is a striking plant that puts up 3-6' tall spikes of white flowers; the flower spikes alone are up to 2' long. Each flower is ~1" long and across with a elongate, triangular bract at the base of the flower pedicel. A short (1/2"), tubular, bluish-green calyx with four triangular teeth encloses the base of a white typical pea-like flower with a forward-leaning banner (one petal, folded up and back along the midline) and a pair of wings (two petals) that enclose a keel (two petals); the keel encloses ten green stamens with orange anthers and the single style.

Baptisia

Baptisia alba

white wild-indigo [Blooms: May-Aug]

Stems of cream wild indigo terminate in 3-9" long flower spikes that sprawl laterally or arch. Each flower is ~1" long and across with a short (1/2"), tubular, light green to light purple calyx with 4-5 triangular teeth, a creamy-yellow (or very yellow) typical pea-like flower with a vertical banner (one petal) and a pair of wings (two petals) that enclose a keel (two petals); the keel encloses ten stamens and the single style. Flowers are held on ~1" long pedicels; at the base of each pedicel, a lance-shaped, 1/2-1" long bract is sessile on the flower stalk. This is our earliest-blooming wild indigo. Flower color, the profuse hairs, and the bracts at the base of each flower pedicel are sufficient to positively identify cream wild indigo.

Baptisia

Baptisia bracteata

cream wild-indigo [Blooms: May-Jun]

Yellow mustard produces inflorescences at the apices of the stems; individual flowers are 3/8" across with four yellowish-green sepals, four yellow petals, six stamens with yellow anthers, and a single pistil with a robust style.

Barbarea

Barbarea vulgaris

yellow rocket [Blooms: Apr-May]

River birch male (left) and female (right) catkins. Individual (highly modified) flowers are distributed over the surface of the catkins.

Betula

Betula nigra

river birch [Blooms: Apr-Jun]

Spanish needles flowers are 1/2" long and 1/4" across; they occur individually on the end of long peduncles. Each flower has 3-5 (sometimes zero) ovoid, yellow, petal-like ray florets around 12-27 yellow, tubular disc florets, each with five small lobes at their tips, 5 stamens, and a bifurcated style. Even in full bloom, the flowers look like buds. After fertilization, each flower produces needle-like, brown, four-angled, barbed seeds, each 1/2-3/4" long, that radiate in all directions from the base of the old flower.

Bidens

Bidens bipinnata

Spanish needles [Blooms: Aug-Sep]

Nodding bur-marigold's flowers usually have eight ray florets ("petals") that are elliptical; the flower is 1-2" across with the flower stem arising from leaf axil. Flowers nod down with age. The phyllaries at the base of the flowers are in two series — the outer phyllaries are of variable length but narrow, curly, and green; the inner phyllaries are almond shaped, as wide as the petals, and pale yellow-green.

Bidens

Bidens cernua

nodding bur-marigold [Blooms: Aug-Oct]

The flowers of devil's beggars-tick consist only of disc florets. The base of the flowerhead is surrounded by 6-10 (usually eight) long phyllaries that extend beyond the flower's edge.

Bidens

Bidens frondosa

devil's beggar-tick [Blooms: Aug-Oct]

Top — Crowned beggar-tick's (Bidens trichosperma) flowers in frontal view. Bottom — about twelve narrow, twisted phyllaries lie below the yellow flower sepals at the top of the stem.

Bidens

Bidens trichosperma

crowned beggar-tick [Blooms: Sep-Oct]

Hairy wood mint flowers consist of (from back to front) a tubular, stubby calyx with five long teeth and margins with very long, soft white hairs; a white or light purple tubular corolla with an unlobed upper lip, hairy on the outer surface; and a three lobed lower lip with scattered purple dots. Two stamens and a pistil with a bifurcated stigma protrude. Upper right — an ant for scale on a hairy wood mint flower.

Blephilia

Blephilia hirsuta

hairy wood mint [Blooms: Jun-Aug]

In black mustard, racemes of yellow flowers arise from the tip of the stems, with the siliques (fruit) of previously fertilized flowers arrayed along the stem below the flowers. The racemes of flowers are 1/2-2" long. Each flower is about 1/3" (8 mm) across, consisting of a short (2-4 mm) pedicel, 4 sepals (green in the buds, turning yellow after the flower opens), 4 yellow, oval to round petals with a narrow base ("claw"), 6 greenish-yellow stamens with yellow anthers, and a green ovary with a short style (which persists in the siliques) at its apex. Fertilized flowers produce smooth, elongate fruits (siliques) 2-3 mm across, approximately four-angled in section, and 1/2-1" long, tapering to a conical or cylindrical beak with the remnant of the style at its tip. The siliques contain 4-15 seeds and are often closely appressed to the stem. The seeds are dark brown or black with networks of furrows on their surface.

Brassica

Brassica nigra

black mustard [Blooms: Jun-Jul]

Individual flowerheads of false boneset are about a half inch long and surrounded by green phyllaries. Each floret (inset) consists of 7-21 creamy-white, tubular florets with five lobes at the tip, and a prominent divided style protruding from the corolla.

Brickellia

Brickellia eupatorioides

false boneset [Blooms: Jul-Aug]

Butterfly-bush has flowers in a elongate cluster (panicle); each flower is trumpet-shaped with an orange center, and the flared end is split into four lobes.

Buddleja

Buddleja davidii

butterfly-bush [Blooms: Aug-Sep]

American searocket's flowers are 3/8" across with four green sepals, four widely spread pale lavender to white petals, six stamens, and a pistil with a single white style.

Cakile

Cakile edentula

American searocket [Blooms: Jun-Aug]

Purple poppy-mallow has hairy flower pedicels ~6" long that arise from leaf axils; the flowers are ~2" across, brilliant magenta, with an hibiscus-like (but shorter) white central structure containing the stamens and styles. The five calyx lobes are very hairy, shorter than the petals, and light green; beneath the calyx are three very similar bracts.

Callirhoe

Callirhoe involucrata

purple poppy-mallow [Blooms: ?-Jul]

The flowers of hedge bindweed are 2-3" long, formed from five white or pink fused petals; the throat of the trumpet is light yellow (less extensive than in field bindweed). The flowers are ephemeral, often lasting only a single day.

Calystegia

Calystegia sepium

hedge bindweed [Blooms: May-Sep]

Wild hyacinth flowers have six slender, light blue to white tepals, six stamens with yellow anthers, and a slender style emerging from a green, egg-shaped ovary; the style has tripartite tip. The flowers are each supported by a slender pedicel. Wild hyacinth is very similar to prairie hyacinth (Camassia angusta), but the latter blooms later, is much less common, has thread-like bracts beneath each flower pedicel, 4-5 thread-like bracts on the flower stalk beneath the flowers, and differ (mostly) in details of the seed capsule. Prairie hyacinth has not yet been found in Jackson Park.

Camassia

Camassia scilloides

wild hyacinth [Blooms: May-Jun]

American bellflower has deep blue flowers with a white center; they are about 1" across. The petals are ruffled, the style is long, arching, with a trifid stigma on its tip.

Campanula

Campanula americana

American bellflower [Blooms: Jul-Aug]

Creeping bellflower stems produce a terminal raceme of blue to purple flowers up to a foot long with all the flowers nodding towards the ground and all on the same side of the stem. Individual flowers are 1-1.5" long, borne on a short pedicel with a narrow, lance-shaped bract at its base. Each flower is bell-shaped with five pointed, recurved lobes with hairy margins and five green sepals at its base. There are 5 short curly, yellow stamens and a long style that emerges from the bell; the style has a three-part stigma at its end.

Campanula

Campanula rapunculoides

creeping bellflower [Blooms: Aug-Sep]

Shepard's purse flowers bloom only at the stem's tip, which is continually elongating. Individual flowers are tiny (1/8") and have 4 greenish sepals, 4 rounded white petals, 6 greenish-yellow stamens, and a pistil with a single style. Flowers are followed by seedpods ("purses") that are 1/4" long, triangular, or heart-shaped, borne on ascending pedicels (lower part of image.)

Capsella

Capsella bursa-pastoris

shepard's purse [Blooms: Apr-May]

Cutleaf toothwort's flowers are ~1/2" across when fully open; the flowers arise from a slender pedicel as long as the flower, 4 green or purple bluntly-pointed sepals <1/3 the length of the petals, four lavender-white petals, six stamens with yellow anthers, and a single pistil with a flat, discoid stigma.

Cardamine

Cardamine concatenata

cutleaf toothwort [Blooms: Apr-May]

Hairy bittercress flower stalks with stem leaves. Here the three flowers bear seedpods (siliques - narrow cylinders) that elongate directly out of fertilized flowers (which continue bear petals).

Cardamine

Cardamine hirsuta

hairy bitter-cress [Blooms: April]

Pennsylvania bittercress flowers are 1/8" across with 4 light green, oblong sepals that cup the corolla, 4 white petals, 6 cream-colored stamens, and a single robust pistil with a flat, disc-shaped stigma. Fruits are erect, elongate (up to 1.25" long and 1 mm wide), flat-ended cylinders (siliques) containing a single row of seeds that emerge from the center of a fertilized flower while the petals persist.

Cardamine

Cardamine pensylvanica

Pennsylvania bitter-cress [Blooms: April]

Nodding thistle is another heavily-defended exotic thistle, accidentally introduced to the U.S in the early 1900s. Solitary flowerheads are borne on long (up to 2'), whitish peduncles densely covered with short hairs. The flowerheads are 1-3" across, nodding (like the name says), made of 100-1000 tubular disk florets, each with its apical portion divided into 5 purplish-pink filaments and with a single, very long style. Beneath the large, showy flowerheads are stout, triangular, purplish phyllaries, each with a stout spine. When in bloom, the large size of the flowers and characteristic large phyllaries make it impossible to confuse with any of our other local thistles. Well loved by goldfinches, but considered a "noxious weed" by almost everyone else.

Carduus

Carduus nutans

nodding thistle [Blooms: Jun-Jul]

Inflorescences of woodland sedge occur as a terminal staminate (male) spike 6-12 mm long and 2-4 ovoid pistillate (female) spikelets 10-20 mm long and 5 mm wide that are lower on the culm. The proximal urn-shaped structures on the inflorescence (and in the inset) with the two fuzzy filaments are the pistillate spikelets; the distal structures with the terminal yellow rods in the image are the staminate spikelets. (Cylindrical clusters of florets are called spikes; ovoid clusters are termed spikelets. Individual sedge flowers — a perigynium or utricle — are usually ovoid, with either 2-3 feathery stigmas or three stamens with anthers sticking out of one end. Bisexual flowers do not occur in sedges.)

Carex

Carex blanda

woodland sedge [Blooms: Apr-May]

Capitate sedge grows 1-2' tall in dense colonies. Each culm (= stem) is triangular in cross section and has an inflorescence about 1.5 cm. long and 1.0 cm. across at its tip. At the base of the inflorescence is a thin leaf (bract) up to 1.5 cm. long. The inflorescence looks like a collection of 5-8 spikey, tightly-clustered tapering stacks (spikelets) of flattened, oval structures sharply pointed at their distal end (the perigynia or florets). Each spikelet measures about 5x5 mm; it contains the actual (highly modified) florets. The male (staminate) florets are located toward the apex of each spikelet (see inflorescence at far left in the image), while the female (pistillate) florets are lower in the spikelet. (Cylindrical clusters of florets are called spikes; ovoid clusters are termed spikelets. Individual sedge flowers — a perigynium or utricle — are usually ovoid, with either 2-3 feathery stigmas or 3 stamens with anthers sticking out of one end. Bisexual flowers do not occur in sedges.)

Carex

Carex cephalophora

capitate sedge [Blooms: May-Jun]

Bottlebrush sedge's fertile stems bear a single, terminal staminate (male) spike up to 3" long and 2-6 pistillate (female) spikes (shown here), each 5-6 cm long and 1.5 cm across. The cylindrical pistillate spikes are comprised of densely packed, female perigynia (florets) radiating from the center of the cylinder.

Carex

Carex comosa

bottlebrush sedge [Blooms: May-Jun]

Gray's sedge is the most easily identifiable sedge in Jackson Park — the large, pistillate (female) spikelet (reminiscent of the head of a medieval mace) is unmistakable. Fertile culms of Gray's sedge may reach up to 3' tall, but most plants don't exceed 2.5'. The culms are triangular in section ("three-angled"), light green and unbranched, with a few alternate, dark green leaves (each 5-14" long and 4-10 mm wide) along its length. The leaves have a deep groove along their midline and, usually, secondary folds on either side, producing a V- or W-shaped cross section in the leaves. Fertile culms produce an Inflorescence at their apex consisting of one or more globoid (mace-like) pistillate spikelets (1-1.5' diameter spiky clusters of perigynia that radiate in all directions) and a single staminate spikelet up to 2.5" long and 1-4 mm wide. Each pistillate spikelet has a 3-10" long leaf at its base. Each perigynum in the pistillate spikelets is quite large (12-18 mm long, 4-8 mm wide), an elongate teardrop (lanceolate) shape, with stigmas emerging from the pointed end. The staminate spikelet is at the tip of the culm on the end of a short pedicle, usually yellow-brown in color. The male and female spikelets are labeled; the long, tan-colored anthers (male) and white stigmas (female) are clearly visible in this image.

Carex

Carex grayi

Gray's sedge [Blooms: May-Jul]

Fertile culms of wood gray sedge produce a terminal inflorescence 6-8" long bearing 2-4 pistillate (female) spikelets and a single staminate (male) spikelet 3/4" long attached beside the topmost pistillate spikelet. Pistillate spikelets are 1-1.5" long and 5 mm across on 3.5 cm long pedicels with a 3-6" long, leaflike bract at their base; there are 5-15 female perigynia in each pistillate spikelet. The perigynia are 4-5.5 mm long, smooth ovoids that are quite inflated, tapering to a blunt tip and base, with easily visible lines ("nerves" - see insert) that run from one end of the perigynum to the other. At the base of each perigynium is a pistillate scale about the same length as the perigynium, narrowing drastically at the free end to a sharp needle ("awn" - see insert). Immature perigynia are green, turning brown with maturity. Wood gray sedge can't be confused with any other sedge that occurs in Jackson Park.

Carex

Carex grisea

wood gray sedge [Blooms: May-Jun]

Fertile culms of porcupine sedge produce an inflorescence at their tips with a single, terminal staminate spikelet and 2-4 pistillate spikelets below balancing on or hanging from thin pedicels. The staminate spikelet is paralleled along its length by a bristly bract; both are up to 2" long. Pistillate spikelets are 0.75-2.5" long and 1/2" across, roughly cylindrical in outline, and packed with widely spreading, inflated perigynia 5-8 mm long and about 2 mm across whose sharp tips give rise to the common name; at their base, the perigynia have a leaf-like bract 4-6" long and 3-4 mm across. The lowest pistillate spikelet has the longest (up to 12") bract. Porcupine sedge is commonly found near the shorelines around the Jackson Park lagoons. Of all the Jackson Park sedges, porcupine sedge is most similar to cyperus sedge (C. pseudocyperus) but has stubbier pistillate spikelets.

Carex

Carex hystericina

porcupine sedge [Blooms: May-Jul]

Troublesome sedge is superficially similar to crested sedge (C. cristatella) but with fewer, less spiky spikelets, and with perigynia less crowded. Two to five (rarely six) spikelets are crowded along an inflorescence at the tip of the culm, each 6-15 mm long and 5-10 mm wide. The perigynia are rounded at tip and base, tapering distally to a blunt point, each with a darker green, winged margin and a lighter center. Staminate (male) perigynia are relatively few and located at the base of the spikelets; most of the perigynia are pistillate (female). At the base of the lowermost spikelet is a thin, bristle-like, usually short bract. The left side of the image shows a young inflorescence; the right side shows a mature inflorescence post-fertilization.

Carex

Carex molesta

troublesome sedge [Blooms: May-Jun]

Sand sedge (Carex muehlenbergii) is a native sedge found throughout the eastern U.S. that grows to 1-2.75 feet tall; it is listed as "vulnerable" in Illinois. The plant consists of several low leaves and a light green culm that is triangular in section ("3-angled"). The leaves are alternate and restricted to the lower quarter to lower third of the culm. The apex of the culms supports an inflorescence 1/2-1.5" long and about 1/2" across consisting of 4-10 overlapping or slightly separated spikelets; at the base of the inflorescence is a 3/4-1" long, slender leafy bract. A spikelet may have either a few male florets at its apex and the perigynia of both male and female florets below or it may consist entirely of female perigynia. Each spikelet is a cluster of 6-16 ascending or widely spreading light green to yellowish brown perigynia, each 3-4 mm long and 2-3 mm wide. The perigynia are oval in profile but flat to convex on one side, tapering to a short beak that ends in two tiny teeth. Each female floret bears a pair of yellowish- to reddish-brown stigmas. The florets are wind pollinated. After fertilization, the perigynia drop off the spikelets and are dispersed by the wind.

Carex

Carex muehlenbergii

sand sedge [Blooms: Apr-May]

Palm sedge fertile culms tend to have fewer leaves (5-10) restricted to the lower half of the culm while infertile culms produce more leaves (8-12+) along their entire length. Fertile culms generate a narrow (5-9 cm long, 1 cm across) inflorescence at their tips bearing 5-12 partially overlapping, stalkless spikelets. Spikelets are 2 cm long, 3-4 mm across prolate spheroids (spindle-shaped); staminate (male) florets are restricted to approximately the bottom quarter of the spikelet while pistillate (female) florets cover the rest of the spikelet. Each spikelet rests on a scale-like bract, only obvious on the lowest spikelet. Perigynia are very large compared to most sedges — 6-8 mm long and about 2 mm across; protruding from the tips of the perigynia are either slender, white styles or pale yellow or white, cylindrical anthers.

Carex

Carex muskingumensis

palm sedge [Blooms: Jun-Jul]

Fertile culms produce a 4-12" long inflorescence at their tip whose central stalk (rachis) is also triangular. Near the tip of the rachis are 1-3 pistillate (male) spikelets 1/2-1.25" long, light green, turning brown with maturity. Below are 2-3 pistillate (female) spikelets each with a leaf-like bract immediately below; the bracts increase in size beneath lower pistillate spikes. The staminate spikelets are usually about 1-3" above the pistillate spikelets, but occasionally appear to grow out of a pistillate spikelet (right). Pistillate spikelets (left) are cylindrical, up to 1.5" long, densely packed with quite hairy, chubby-triangular, perigynia (each 2.5-4" long and about half as wide), and their accompanying bristly bracts. The plants are wind pollinated. Wooly sedge is unusual in its very hairy perigynia; no other Jackson Park sedge has this character.

Carex

Carex pellita

woolly sedge [Blooms: Apr-May]

Fertile culms of Pennsylvania sedge produce an apical inflorescence with a single terminal staminate spikelet 1-2.5 cm long above 1-3 smaller pistillate spikelets and their bracts, all purplish-brown at blooming. Staminate spikelets produce prominent creamy-yellow anthers; pistillate spikelets consist of 4-12 perigynia about 3 mm long and 1.5 mm across, each with 3 white, thread-like styles and a basal, scale-like bract shorter than the spikelet. The lowest pistillate spike bears a basal leaf-like bract usually longer than the spikelet. Florets are wind pollinated.

Carex

Carex pensylvanica

Pennsylvania sedge [Blooms: Apr]

Cyperus sedge's fertile culms develop an inflorescence at their tips 1.5-6" long consisting of a single staminate spikelet up to 3" long and 2-6 pistillate spikelets 3" long and 9-12 mm across. The pistillate spikelets are initially erect but later droop (especially the lowest pistillate spike, which has the longest pedicle). At the base of each pistillate spike's pedicle is a leaf-like bract up to 20" long. Perigynia of the pistillate spikes are oriented perpendicular to the axis of the cylindrical spikelet, 3.5-6 mm long and 1-2 mm wide, not inflated, lance-shaped with two strong 1 mm long teeth at their tips. (Insert) - Three fuzzy stigmas protrude from the tips of the perigynia.

Carex

Carex pseudocyperus

cyperus sedge [Blooms: Jun-Jul]

A fertile culm of star sedge (right). Most culms are fertile, generating an apical inflorescence 1.5-3" long with 3-8 spikelets more closely spaced the higher their position on the inflorescence. Spikelets consist of 1-9 perigynia, 3 mm long and 1.5 mm wide, each initially erect, but later rotating so they point in all directions. (Thus, the species name "radiata.") At the base of each spikelet is a needle-like, long, narrow bract. The bracts are longer the further the spike is from the tip of the inflorescence; the bract beneath the most basal spikelet may be as long as the entire inflorescence. The male florets (lower left image; note the club-like anthers) occur above (more distal than) the female florets in the spikelet; the latter have a pair of 1 mm long styles protruding from their tips (upper left image; the fuzzy stigmas are beginning to wither in this image).

Carex

Carex radiata

star sedge [Blooms: May-?]

Rosy sedge (Carex rosea) is a native perennial sedge that typically grows 8-12" tall but individual culms may get as long as three feet. Culms are three sided ("three square"), 1.6-2.2 mm wide basally, tapering to 0.5-0.9 mm distally; the upper parts of the culm are rough textured. Spikes are stalkless and occur in a cluster at the tip of the culm up to 2.75" long. The cluster is composed of 4-8 small spikelets, crowded at the tip of the spike but well separated lower in the spike. Individual spikes consist of staminate (male) florets at the tip and pistillate (female) florets at the base, the individual florets radiating in all directions from the center of the spike. At the base of each spike is a bristle-like bract; the lowest bract in the cluster may be more leaf-like and may overtop the terminal spike. The staminate florets have anthers 0.8-1.3 mm long. The pistillate spikes produce fruit in late spring or early summer that consists of clusters of seeds (achenes) 1.6-2.2mm long and 1.1-1.6 mm wide. The pistillate scales are 1.3-2.75 mm long. The perigynia are 2.6-4 mm long and 1.1-1.8 mm wide, green to yellowish brown at maturity, lance-shaped in outline and flattened on the back; they taper to a short beak with minute teeth along the edges and two larger teeth at the tip. The styles often persist in the fruit with the two twisted stigmas protruding. Each cluster of seeds is wrapped in a casing (perigynium) and subtended by an egg-shaped to nearly round pistillate scale, translucent white with a green midrib, blunt or pointed at the tip but lacking an awn. You're unlikely to confuse rosy sedge with any of the other local sedges except the star sedge (Carex radiata) which also has culms that are triangular in section and, late in the development of the inflorescence, also has a "starburst" pattern of spikelets radiating in all directions. Star sedge has narrower (<2 mm) leaves than rosy sedge (3 mm) and star sedge has straight styles while rosy sedge has styles that curl through three turns; the styles in both species are red (assuming the styles are in their prime when you see them). Compare photos of the two species before deciding on an identification.

Carex

Carex rosea

rosy sedge [Blooms: May-Jun]

Fertile culms produce an apical inflorescence up to 12" long bearing 1-3 staminate (male) spikelets 1-2 cm long with 3 anthers and 2-5 pistillate (female) spikelets 1.5-3 cm long. The pistillate spikelets are roughly cylindrical overall with 10-30 perigynia 4-7 mm long radiating in all directions from the axis; each perigynium has an inflated, nearly-spherical base and a long, tapering, sharp distal beak.

Carex

Carex sprengelii

longbeaked sedge [Blooms: Apr-May]

Two prickly sedge inflorescences photographed about a month apart. Fertile culms bear an apical inflorescence from 2-4" long bearing several short spikelets with a distinctly spikey appearance; the spikelets are initially light green (left image) but turn gold (right image) to brown as they mature. Each spikelet has a needle-like bract at its base (longest in the lowermost spikelet); the spikelet has a few staminate (male) perigynia apically but the majority of the perigynia are pistillate.

Carex

Carex stipata

prickly sedge [Blooms: May-Jun]

Blunt broom sedge (Carex tribuloides) is a native perennial that ranges across the eastern half of the U.S. It is classified as "Secure" in Illinois although it is not very common in Jackson Park. The culms of blunt broom sedge range from 1.5-3 feet long, erect or (more often) ascending. In tufts of blunt broom sedge, both sterile and fertile culms appear; both are light green, hairless, and triangular ("3-angled") in cross section. Fertile culms carry a 2.5" long inflorescence at their tips consisting of 5-15 partly overlapping or slightly separated spikelets. In contrast to the usual pattern in sedges, the spikelets of blunt broom sedges bear male (staminate) florets at their bases and female (pistillate) florets distally, the latter with two protruding stigmas. Individual spikelets are stalkless, 6-12 mm long, ovoid, and markedly prickly due to the long beaks of the ascending perigynia (which are 3-5 mm long and 1.25-1.75 mm across, flattened, and lance-shaped). The spikelets are cone-shaped in outline, tapered at their base and rounded at their tips. Immature spikelets are light green; mature spikelets are light brown. The lowest spikelet in an inflorescence has a 1/2-3/4" long, needle-like bract at its base; the next higher spikelet may also have a (shorter) bract at its base. The florets are wind pollinated. Blunt broom sedge prefers moist to wet conditions in light shade to full sun, favoring habitats like wet meadows, floodplain forests, pond margins, and swamps.

Carex

Carex tribuloides

blunt broom sedge [Blooms: May-Jun]

Brown fox sedge fertile culms apically bear a 2-5" long, 15 mm wide inflorescence (bottom) with numerous spikelets variably spaced along the axis. All spikelets have staminate (male) flowers apically and pistillate flowers below with a bristle-like bract at their bases; the lowest bract is the longest (up to 2"). Perigynia (top) are 2-3 mm long and 1.5 mm across, tapering to a toothed beak; pistillate scales as long as the perigynia with terminal awns add to the bristly appearance.

Carex

Carex vulpinoidea

brown fox sedge [Blooms: May-Jul]

Pecan trees have separate male and female flowers on the same tree. The staminate (male) catkins droop from short spurs on the twigs; they typically develop in groups of three and are about 4-6" long with numerous staminate florets along the catkin. Individual staminate florets have a three lobed bractlet arising from their base that shelter the 4-6 stamens that hang beneath it; the middle lobe is the longer of the three lobes. The pistillate (female) spikes develop at the tips of a subset of the twigs, each spike bearing 3-10 greenish, pistillate florets; the florets are 1/4" long and 1/8" across. Each pistillate floret contains a short, tubular calyx, four bractlets of unequal sizes, and a pistil with two feathery stigmas. Each bractlet has four erect to spreading, lance-shaped lobes. The pistillate florets are wind pollinated. Fertilized florets transform into 2-6 greenish fruits (nuts in a husk) in a cluster, each with four short wings; when mature, the ovoid fruits are about 2" long and 1" across, brown or black in color; the husks partially divide into four segments along the wings, releasing the nut. Pecan is typically a bottomland tree that lives in river valleys but can grow in any rich, moist, well-drained soil. The leaves of black walnut and pecan have a similar number of leaflets in their odd-pinnate leaves, but the fruits are completely different. According to the Arnold Arboretum at Harvard, pecan trees (Carya illinoinensis) can live for over 300 years. For some reason, Carya illinoinensis is the state tree of ...... Texas.

Carya

Carya illinoinensis

pecan [Blooms: Jun-Aug]

Northern catalpa's inflorescence is a pyramidal panicle with 10-30 flowers. Individual flowers are large (~2" across) and trumpet-shaped with two lobes, bright white with purple lines leading towards the corolla's center; two yellow-orange spots are present on the lower lateral edges of the corolla's opening. Two fertile and three sterile stamens, and a single, white style with a bifurcated stigma are present.

Catalpa

Catalpa speciosa

Northern catalpa [Blooms: Jun-Jul]

At the apex of the blue cohosh stem is a floral panicle 1-3" long bearing 5-30 flowers. Individual flowers (insert) are about 1/3" (8 mm) across with six petal-like yellow-green sepals, and six stamens with yellow anthers in a ring around a central green ovary and style. The petals have been reduced to six green lobes at the base of the stamens, between the sepals.

Caulophyllum

Caulophyllum thalictroides

blue cohosh [Blooms: Apr-May]

New Jersey tea flowers occur in panicles ("puffballs") up to 5" long and 3" across on peduncles up to 8" long arising from the tip of stems or axils of a leaf. Flowers are 1/4-3/8" across on 1/4-3/4" stalks; each flower has five triangular white sepals folded inwards towards the flower center; five widely spreading, white spoon-shaped petals with narrow bases and broad tips (tips curled in to heighten the "spoon" impression) emerging from between the incurled sepals; five stamens with whitish-purple anthers; and a three-part style.

Ceanothus

Ceanothus americanus

New Jersey tea [Blooms: Jun-Jul]

American bittersweet side branches occasionally produce panicles of flowers (up to 6" long) at their tips. Male flowers are about 1/4" wide with five light green petals with jagged or undulate margins, five green sepals, and five stamens with yellow anthers and a narrow style rudiment.

Celastrus

Celastrus scandens

American bittersweet [Blooms: Jun-Jul]

Common hackberry flowers may be staminate (male), pistillate (female), or perfect (both), all on the same tree. Flowers are about 1/4" across and bloom before the leaves open, often high in the tree (thus, I have no pictures yet). All flowers are wind-pollinated, yellowish-green with 4-6 spreading sepals joined at their bases; there are no petals. Male flowers have 4-5 stamens with green or yellow-brown anthers; female flowers have a green ovary with a large two-part, densely fuzzy style like an umbrella beneath the ovary. Perfect flowers have both.

Celtis

Celtis occidentalis

common hackberry [Blooms: Apr-May]

Sandburs are no one's friend. They are a form of grass with light green culms, round in section, up to 2.5' long; they are mostly covered by the sheaths of the alternate leaves. Each culm and upper branches (if any) terminate in a 4" long (3/4" across) raceme of 4-20 spiky burs. Each 1/4" diameter bur (excluding the spines) consists of 2-3 spikelets, each containing a fertile flower recognizable only by the stamens or styles protruding from the tip of the spikelets. The flowers are wind pollinated. This is the only sandbur in Illinois, so identification is easy (if not always painless).

Cenchrus

Cenchrus longispinus

sandbur [Blooms: Aug-?]

Spotted knapweed has pink to purplish flowers ~3/4" across composed of numerous tubular, branching, sterile ray florets with five lobes; the outermost ray florets are the longest. Disc florets ARE present, shorter and more erect than the ray florets but similar in appearance, with pink to white-tipped anthers and a divided style. The urn-shaped base of the flower is covered with tightly appressed oval bracts, each green with black tips; long, comb-like pale bristles radiate from the tip giving an appearance rather like a tick (inset).

Centaurea

Centaurea stoebe

spotted knapweed [Blooms: Jun-Sep]

Buttonbush is a shrub with golfball-sized white inflorescences studded with long, protruding styles — distinctive and unmistakable. Flowering stalks produce 1-3 spherical flowerheads 3/4-1.5" across completely covered with 100-200 small white flowers. Individual flowers are small (1/3" long), white, with four (sometimes five) lobes at the apex; stamens are short while the styles are very long (~3/8"), yellow-tipped, and projecting well beyond the corolla. Maturing seedheads are bright red, but turn brown when fully ripe.

Cephalanthus

Cephalanthus occidentalis

buttonbush [Blooms: Jun-Jul]

Mouse-ear chickweed has stems up to 1.5' long with long, spreading hairs; the flower stalks and sepals are also covered with fine hairs. The flowers are tiny (<1/4") with five white petals that have deeply notched tips, five sepals as long as the petals, five styles emerging from a green central ovary and ten stamens with yellow anthers. (Other chickweeds have three styles.)

Cerastium

Cerastium fontanum

mouse-ear chickweed [Blooms: Apr-May]

Clusters of 4-8 flowers begin to bloom before the leaves emerge on Eastern redbud; the buds (lower left) are rosy-pink, turning a lighter pink when the flowers open. Individual flowers are about 1/2" long, on pedicels 1/4-1/2" long, pea-like with an upper central petal (the banner), two upper lateral petals (the wings) and two lower petals (usually a darker pink) that form the projecting keel; a short purplish tubular calyx with five blunt teeth lies behind the corolla. The keel encloses ten stamens and a single curved style.

Cercis

Cercis canadensis

Eastern redbud [Blooms: Apr-May]

Wild chervil upper stems terminate in up to three clusters of 3-7 small, white flowers (right image). Individual flowers (upper left) are tiny (1/8" across), each with five white petals, five stamens, and a cylindrical green ovary bearing a split style; the sepals are highly reduced. After fertilization, both the cylindrical ovary and the flower stalk elongate; mature fruits (lower left) are usually hairless, about 1/4" long, and contain a single seed.

Chaerophyllum

Chaerophyllum procumbens

wild chervil [Blooms: May-?]

Partridge pea flowers are ~1" across, noticeably asymmetric, with five yellow petals with red blotches at their base; the lowermost petal is about twice the size of the other petals. One of the lateral petals curls around the stamens. There are ten reddish-purple stamens and a single greenish-yellow style (longer than the stamens) that curves upward towards the tip; nine smaller stamens lie on one side of the style and one larger stamen on the other.

Chamaecrista

Chamaecrista fasciculata

partridge pea [Blooms: Jul-Oct]

White turtlehead flowers are ~1-1.5" long with a few basal green sepal-like bracts and a green calyx bearing five oval teeth with rounded tips. The cavernous tubular, creamy-white corolla has two large lips — the two-lobed upper lip functions as a hood, while the three-lobed lower lip, "bearded" with wooly hairs, functions as a landing area for pollinators. Inside the corolla is a slim white style that runs along the inside of the upper lobe but turns down sharply at the lip, and five hairy stamens (one of which is green and sterile).

Chelone

Chelone glabra

white turtlehead [Blooms: Sep-Oct]

Lamb's quarters produces inconspicuous star-shaped, yellow-green flowers, <1/8" across, sessile on flower stalks in round, tight clusters; the flowers have no petals, five stamens with yellow anthers, and a single divided style at the tip of a round, green ovary, all cupped in a five-lobed, mealy-white, calyx. The flowers are wind-pollinated and can aggravate hay fever symptoms.

Chenopodium

Chenopodium album

lamb's quarters [Blooms: Jul-Sep]

Glory-of-the-snow produces a flower stalk 6-12" tall, topped by a one-sided raceme of 4-10 upward-facing flowers. Individual flowers are 1/2-3/4" wide and have six pastel violet-blue tepals with white bases; the bases of the stamens are flattened and form a palisade around the middle of the flower. ITIS shows Chionodoxa forbesii as the accepted name; World Flora Online accepts Scilla forbesii.

Chionodoxa

Chionodoxa forbesii

glory-of-the-snow [Blooms: Mar-Apr]

Chicory flowerheads are an unmistakable clear blue, 1-1.5" across, sessile or on very short stalks, with 10-20 (typically 17) blue ray florets with five tiny teeth at their tips; there are no disc florets. Two series of small bracts covered with glandular hairs cup the base of the flowerhead. In the center of the flowerhead are spike-like, deep-blue stamens (one for each ray floret) fused around a style, each style with a light blue, bifurcated stigma. The flowerheads open in the morning but usually close later in the day.

Cichorium

Cichorium intybus

chicory [Blooms: Jun-Sep]

Enchanter's nightshade produces a raceme of scattered white flowers, 1/8-1/4" across; the flowers have two (deeply notched but otherwise quite pedestrian) white petals, two green sepals at 90° to the petals, two stamens, and a single slender style. At the base of the flower (behind the sepals) is an egg shaped, swollen green ovary; the ovary and the pedicels of the flowers are covered with long, hooked, white hairs. The fruit is a teardrop-shaped, bur-like remnant of the ovary; it contains two seeds. There is no other local plant that could be confused with this species.

Circaea

Circaea canadensis

enchanter's nightshade [Blooms: Jun-Jul]

"Canada thistle" is a calumny on poor Canada; this homely plant is native to Eurasia, not our northern neighbor. Flowerheads of Canada thistle are much smaller (1/2-3/4" across) than those of bull or field thistle and often occur in clusters on the plant. The involucre is goblet- rather than vase-shaped, covered by closely appressed green to purplish phyllaries, that have short, sharp, brown tips but no spines; there are only tubular disk florets with five thread-like, 1/4" long apical lobes, pink or pale lavender (rarely white) in color.

Cirsium

Cirsium arvense

Canada thistle [Blooms: May-Sep]

Field thistle is a native weedy plant often found in disturbed areas, up to 8' tall, but usually much shorter. Flowerheads occur on the tips of branches, are light pink, and about 2" across. The base (involucre) of the flowerhead is vase-shaped and covered with multiple series of closely appressed, overlapping phyllaries/bracts (often said to look like fish scales). Each bract has a a medial white line and a single, sharp, 1/4" long golden spine at the tip. Below the involucre are a few slender bracts that look like miniature versions of the stem leaves; these bracts curve upwards around the flowerhead.

Cirsium

Cirsium discolor

field thistle [Blooms: Aug-Sep]

The base (involucre) of the 1.5-2" wide flowerhead of bull thistle is vase-shaped and covered with numerous series of imbricated, spreading phyllaries/bracts that taper into stiff, sharp points. The upper portion of the flowerhead consists of numerous pinkish-purple to purple tubular disk florets that split apically into five thread-like lobes and a single protruding style. This is the only North American thistle with spines (albeit, short) on the upper surface of the leaves and one of the few with spreading, spiny bracts at the base of the flowerhead; native thistles lack spines on the stems.

Cirsium

Cirsium vulgare

bull thistle [Blooms: Jun-Aug]

The flowers of both Claytonia caroliniana and Claytonia virginica occur in clusters (racemes) of 2-10 at the tip of the stem and are small (1/3-1/2") with long flower stalks. The flowers of both species contain (only) two green sepals; five petals with pinkish-purple stripes on a white background; five stamens with deeply purplish-pink anthers; and a single style that splits into three above its midpoint. The flowers of both species close at night or on cloudy days and nod down; they perk up and reopen when the light increases. The fruit of both species is a three-part, egg-shaped capsule nestled between the two sepals. Each capsule contains 1-6 shiny, black seeds 2-4 mm long which have a coating that attracts ants; the ants carry the seed off to their nests, thus dispersing them.

Claytonia

Claytonia caroliniana

Carolina spring beauty [Blooms: Apr]

Spring beauty flowers occur in a cluster of 2-10 at the tip of the stem. The flowers are small (1/3-1/2") with long flower stalks; they contain (only) two green sepals, five petals with pinkish-purple stripes on a white background, five stamens with deeply purplish-pink anthers, and a single style that splits into three above its midpoint. The flowers close at night and on cloudy days and nod down; they perk up on reopening. The fruit is an three-part, egg-shaped capsule nestled between the two sepals.

Claytonia

Claytonia virginica

spring beauty [Blooms: Apr-May]

Asiatic dayflower flowers are 0.5-1" across; they have two thin, blue upper petals and a single, lower, translucent white petal with three lobes. There are 5-6 long stamens with yellow anthers highlighted by a central dot of maroon; the upper three stamens are sterile and probably only serve as an advertisement, while the lower two bear larger anthers with viable pollen. A single long style lies below the stamens. Below and behind the flower is a leaf-like bract (spathe) 1-2" long that is open to its base and embraces the flower like a hammock.

Commelina

Commelina communis

asiatic dayflower [Blooms: Jun-Oct]

Upper stems of poison hemlock bear compound umbels 2-5" wide of tiny (1/8") white flowers with five spoon-shaped petals (one often larger than the others), usually with a longitudinal fold and notched; below the umbels are oval bracts with elongate tips, not divided like the leaves.

Conium

Conium maculatum

poison hemlock [Blooms: May-Jun]

Lily-of-the-valley's raceme bears 6-14 bell-shaped, 8 mm long (and wide), white flowers on one side of the stalk; it often nods at its tip. Individual flowers are bell-shaped with six recurved, pointed lobes around the mouth, white to light green, with six stamens and a single style with a three-lobed stigma hidden inside. The corolla is pendant, dangling from the raceme by 1/2" long, flexible pedicels that have light green, narrow bracts about as long as the flowers at their base.

Convallaria

Convallaria majalis

lily-of-the-valley [Blooms: Apr-May]

Field bindweed stems produce 1-4 funnel-shaped flowers, each arising from a leaf axil, about 1" across and cupped by five small sepals and attached to a flower stalk; the flower stalk bears two small bracts about 1" below the base of the flower. Flowers range from white to pink, with a clear yellow center containing five stamens and a single style with a split stigma. Each bloom lasts only one day.

Convolvulus

Convolvulus arvensis

field bindweed [Blooms: May-Aug]

Horseweed flowering stems form a pyramidal inflorescence covered with numerous flowers and what look like dandelion seedheads. Panicles of flowers up to 1.5' long 6" across arise from the tip of the main stem and from axillary stems that arise from the upper leaves. Individual flowers are small (~1/8" in diameter and 1/4" long), cylindrical or urn-shaped, and covered with multiple layers of phyllaries; they look more like buds than flowers with only the tips of the 25-45 white or pink, pistillate ray florets peeking out the end. The 12-25 disk florets are yellow; they bear both pistils and stamens.

Conyza

Conyza canadensis

horseweed [Blooms: Jul-Aug]

Lance-leafed coreopsis flowerheads are 2-3" across; they have about eight broad, yellow ray florets with 3-5 (usually four) bold, sawtooth lobes at their tips (that may also be subdivided); the numerous disk florets are also yellow, tubular, about 1/4" long with 4-5 tiny lobes. The seeds are black, egg-shaped, and 2.5-5 mm long with thin papery wings along the edges.

Coreopsis

Coreopsis lanceolata

lance-leafed coreopsis [Blooms: May-Jun]

Prairie coreopsis flowerheads occur alone or in pairs on 1/2-2" long peduncles attached to the ends of stems. Each flowerhead is about 2" across with 8-12 ray florets; two prominent longitudinal veins divide each ray floret petal into thirds. The disc florets are tubular with 4-5 lobes; they are initially yellow, but turn brownish with age.

Coreopsis

Coreopsis palmata

prairie coreopsis [Blooms: Jun-Jul]

Plains coreopsis flowers are 1-2" across, with 6-12 (usually 8) ray florets, each with three lobes at their tips (center largest). The ray florets are sterile, typically yellow at their tips, transitioning abruptly to a maroon color more basally. The disk florets are perfect (have both anthers and pistils), reddish-brown to maroon with the florets at the edge of the disc with bright yellow highlights (either the anthers on the fused stamens or the split stigma of the pistils); individual florets have four teeth/lobes. The involucre of the flowerhead is often reddish-tinged, particularly obvious when cupping the developing seedhead.

Coreopsis

Coreopsis tinctoria

plains coreopsis [Blooms: Jun-Oct]

Tall coreopsis flowerheads arise from peduncles up to 10" long; the flowerheads are 1.5-2" across with eight sterile, yellow ray florets (each with two deep folds that divide the ray florets longitudinally into thirds) and numerous reddish-purple, fertile disk florets. The corollas of the disc florets are tubular, with 4-5 triangular lobes at their tips, and about 5 mm (~1/4") long; each has five stamens (fused together at their tips) with yellow anthers, and a single bifurcated style with pointed tips.

Coreopsis

Coreopsis tripteris

tall coreopsis [Blooms: Aug-Sep]

Whorled coreopsis' flowerheads are a bright golden yellow, 1-2" across, with eight yellow, elongate egg-shaped ray flowers and numerous (30-40) yellow disk flowers.

Coreopsis

Coreopsis verticillata

whorled coreopsis [Blooms: Jun-Sep]

Silky dogwood flowers occur in flat to convex clusters (cymes) 1-2.5" across. Individual flowers are about 3/8" across with four sharp sepals, four creamy-white, lance-like petals, four stamens about as long as the petals, and a single, stout, green-tipped style arising from an amber ovary. The flower stalks are silky-hairy.

Cornus

Cornus amomum

silky dogwood [Blooms: May-Jun]

Rough-leaved dogwood is a shrub/tree that can be as much as 20' tall. Cymes of white flowers 2-4" across arise from the leaf axils; the upper bounding surface of the cyme is flat or gently rounded. The fruit (a drupe) is white, about 1/4" across, and spherical; as it ripens, the branches of the cyme turn deep red. The fruit is very attractive to wildlife.

Cornus

Cornus drummondii

rough-leaved dogwood [Blooms: ?]

Cornelian cherry dogwood is a European exotic that has been planted in Jackson Park. Flowers appear in umbels before the leaves emerge. The flowers are small (1/8"), with four bright yellow, lance-shaped petals, four stamens, and a cone-shaped, hairy receptacle; the single pistil emerges from the center of the ovaries. The fruit is an oblong, dark red drupe about an inch long.

Cornus

Cornus mas

Cornelian cherry dogwood [Blooms: Apr-?]

Swamp dogwood's flat-topped panicles of flowers are 2-3.5" across. Single flowers are about 1/4" across with a light green, tubular calyx, four lance-shaped white petals, four stamens, and a single style.

Cornus

Cornus obliqua

swamp dogwood [Blooms: Apr-Jun]

Gray dogwood flowers occur in dome-shaped panicles with creamy-white branches 1.5-2.5" across and tall. Individual flowers are 1/4" across with a short calyx bearing four short teeth, four lance-shaped, creamy-white petals, four stamenns with pale yellow anthers, and a central, green-tipped style. The fruit is a small (1/4"), ball-shaped drupe, white when mature; when the fruit is mature, the branches of the panicle turn from white to bright red. Rough-leaved dogwood and red-osier dogwood also produce white fruit, but their panicles are flat-topped, not domed; the panicle branches are also not red in red-osier dogwood, but they are in rough-leaved dogwood so carefully inspect the stems (hairy) to see if the specimen in hand might be the latter.

Cornus

Cornus racemosa

gray dogwood [Blooms: May-Jun]

Red-osier dogwood flowers occur in flat-topped or slightly concave panicles 2-3" across; each flower is about 1/4" across with a small green calyx with four teeth; four white, lance-shaped petals; four stamens longer than the petals; and a single style rising from a reddish ovary. The fruit is a drupe about 1/4" across, white at maturity; the panicle branches remain green (unlike gray dogwood where the panicle branches turn red).

Cornus

Cornus sericea

red-osier dogwood [Blooms: Apr-Sep]

American hazelnut flowers. The male inflorescence is a cylindrical catkin that appears in the fall on the most recent year's twigs and then overwinters; in the spring, the catkin elongates (to 2-4" long) and the male flowers (consisting of two tiny bracts and four stamens) open to release their pollen. The female inflorescence looks like a small bud protected by bracts that is located at the branch tip or in leaf axils; it contains several pistillate flowers seen only as red styles/stigmas protruding from the tip of the "bud."

Corylus

Corylus americana

American hazelnut [Blooms: Mar-Apr]

Cockspur hawthorn produces flat-topped panicles of flowers 2-3" across that arise from leaf axils; the panicle branches are light green and hairless. Individual flowers are 1/2" across; they have a green calyx with five teeth, five spreading white petals, 10-20 stamens with pink or pale-yellow anthers, and a pistil with 2-3 styles. At least in Jackson Park, the upper surface of the receptacle at the base of the pistil is a shiny greenish-yellow to reddish-yellow. The flower's scent is not pleasant to humans but bees and syrphid flies are not deterred. The fruit is a small (1/2" across) crabapple-like pome, red at maturity.

Crataegus

Crataegus crus-galli

cockspur hawthorn [Blooms: May-Jun]

Downy hawthorn produces clusters of 5-17 flowers; the flower stalks are reddish-green and hairy. Individual flowers are 3/4-1" across with five green, triangular sepals with glandular hairs along the margins that are fused at their base; five round, white petals; 17-20 stamens with pale yellow or white anthers; and 4-5 styles. In Jackson Park, the top of the receptacle (at the center of the flower around the bases of the styles) is reddish-green to deep red and shiny.

Crataegus

Crataegus mollis

downy hawthorn [Blooms: Apr-May]

Common hawthorn produces broad, dense, flattened clusters (cymes) of five to fifteen flowers. Individual flowers are up to 1/2" wide with five reflexed sepals, five white petals, 15-20 stamens with red to purple anthers, and a single style. At least in Jackson Park, the upper surface of the receptacle at the base of the pistil is a shiny yellowish green.

Crataegus

Crataegus monogyna

common hawthorn [Blooms: May-?]

Narrow-leaf hawksbeard is a weedy-looking plant that reaches a size of 8-40". Flowers occur in a panicle (usually arising from a leaf axil) with up to 20 dandelion-like flowerheads. Individual flowerheads are about 1" across with 30-70 yellow ray florets (the "petals"); beneath the ray florets are two layers of green bracts — an inner layer of 12-15 3/8" long, sharply-pointed, keeled bracts covered in wooly or short stiff hairs and an outer layer of bracts half the length of the inner layer, sometimes ridged, with hairs like the inner layer. Narrow-leaf hawksbeard can be distinguished from similar dandelion-like flowers (Crepis pulchera, Crepis capillaris, and various sowthistles and hawksweeds) by the presence of auricles on the stem leaves and a layer of appressed hairs on the inside surface of the inner bracts, best seen with a magnifier.

Crepis

Crepis tectorum

narrow-leaf hawksbeard [Blooms: May-?]

Spring crocus (Crocus vernus) is native to alpine regions of Europe, but widely escaped from domestic gardens in the U.S. Given its early blooming and short duration, it probably qualifies as a "spring ephemeral." The plant is short (4-6") but blooms before most other plants emerge. the leaves are 3-6" long and less than 1/4" wide, dark green with a distinctive silver-white medial stripe. Flowers are up to 6" tall, bell-shaped, 1-1.5" wide with six white to purple tepals in two overlapping whorls of three; the stamens are white with long yellow or orange anthers, the styles are yellow-orange, three-lobed, with a fringe of narrow processes. You'll know it when you see it.

Crocus

Crocus vernus

spring crocus [Blooms: Mar-Apr]

Honewort's inflorescence is a compound umbel 1.5-3" across of tiny (1/8") flowers. Each flower has five stamens with creamy-yellow anthers, and one or two light green, conical pistils; the five petals are usually curled in. In Jackson Park, flowers of honewort have two conical styles, whitish to greenish, that are shorter than the petals.

Cryptotaenia

Cryptotaenia canadensis

honewort [Blooms: May-Jun]

Winged pigweed flowers are whitish-green, sessile, and 1/16" across; the flowers have five inward-curving sepals that cover the ovaries, five stamens, and a flattened ovary with 2-3 styles. Flowers may contain only a pistil or both a pistil and stamens; if the latter, the creamy-yellow anthers are prominent.

Cycloloma

Cycloloma atriplicifolium

winged pigweed [Blooms: Jul-Aug]

Shining flatsedge is an attractive plant up to 10" tall with sprawling culms up to 8" long, triangular in section. The flower spike (inflorescence) has 2-7 strikingly laterally-flattened spikelets 1/4-1/2" long; each spikelet has 8-18 reddish-brown floral scales arranged in two opposing rows, each covering a floret consisting of 2-3 stamens, an ovary, and a split style which may protrude 1-2 mm beyond the scales. The plant is wind pollinated.

Cyperus

Cyperus bipartitus

shining flatsedge [Blooms: Aug-Sep]

Yellow nut sedge flower spikes are 2-3" long with spikelets sticking out at 90° to the axis and 90° to each other around the axis (producing four somewhat irregular rows down the axis). The axis itself is flattened with narrow wings. Individual spikelets are 1/2-3/4" long, yellow- or golden-brown, flattened, with from10-30, 2-3 mm long scales, each covering a floret. Each floret has a white, tripartite style with curly ends (the stigmas) and three stamens with yellowish-brown anthers; the flowers are wind pollinated.

Cyperus

Cyperus esculentus

yellow nut sedge [Blooms: Aug-?]

Rusty flatsedge produces an umbel comprised of 3-6 floral stalks 1-4" long bearing clusters of 2-4 floral spikes. (Visually, this looks much like the branch of a fir tree.) Individual spikes are 1/2-1.5" long with individual needle-like spikelets 1/2-1" long pointing in all directions (like a bottle brush). Each spikelet has 8-25 scales sheltering perfect florets (i.e., both three stamens and a tripartite style are present). Spikelets are initially yellow- or whitish green, becoming reddish-brown at maturity. (Thus the "rusty" name.)

Cyperus

Cyperus odoratus

rusty flatsedge [Blooms: Aug-Sep]

White prairie-clover produces 1-3" long spikes of flowers and flower buds which open progressively from the base of the spike to the tip. Individual flowers are tiny (about 1/4" across), pea-like, white, with five petals (one much larger than the other four); five white stamens with pale yellow anthers protrude beyond the edge of the flowers.

Dalea

Dalea candida

white prairie-clover [Blooms: Jun-Jul]

At the apex of a purple prairie-clover stem is a 1-2.5" long spike of flowers and flower buds which open progressively from the base of the spike to the tip. Individual flowers are tiny (1/4" across), pea-like, deep magenta in color, with five purple petals (one much larger than the other four). Five stamens with golden anthers protrude beyond the edge of the flowers.

Dalea

Dalea purpurea

purple prairie-clover [Blooms: Jun-Aug]

Shrubby cinquefoil flowers are 3/4-1.5" across, bright yellow, with petals that are circular and overlap, 15-20 stamens with golden anthers, and numerous pistils clumped in the center. The five sepals are largely hidden behind the petals; only the sepal's tips protrude.

Dasiphora

Dasiphora fruticosa

shrubby cinquefoil [Blooms: May-Jul]

Mullein foxglove has an odd-looking but very attractive flower that always makes me think of Burt Lahr's Cowardly Lion in the (1939) Wizard of Oz. Individual flowers are about 1/2-3/4" long and across with a basal green calyx decorated with five blunt teeth. The bright yellow, tubular corolla terminates in five spreading lobes; the upper two lobes are reflected backwards, while the lower three lobes (presumably) function as a landing pad for pollinators (mostly bumblebees). From the front, the opening into the corolla is largely obscured by numerous fine yellow hairs that tend to hide the stamens (present in two distinct lengths) and the single style with a two-lobed stigma.

Dasistoma

Dasistoma macrophylla

mullein foxglove [Blooms: Jul-Aug]

Queen Anne's lace is probably the most widely known exotic, a plant introduced from Europe. The inflorescences are the familiar flat compound umbels 2-5" across made up of hundreds of tiny flowers; beneath the umbel are bracts up to 2.5" long, very narrow, and superficially pinnate with three or more lobes. Individual flowers are <1/8" across, with five white petals, a reddish ovary topped by two white styles, and five white stamens. Flowers near the edge of umbels are often asymmetrical, with the petals towards the free edge larger. Not uncommonly, a single flower in the center of the compound umbel has reddish-purple to nearly black petals. The fruit is a ribbed seed with long stiff hairs along the ribs; the entire umbel closes over the immature fruits like a fist to protect them as they mature.

Daucus

Daucus carota

Queen Anne's lace [Blooms: Jun-Aug]

Decodon verticillatus

Decodon

Decodon verticillatus

swamp loosestrife [Blooms: Jul-Aug]

Illinois bundleflower flowerheads are about 1/2" across; they contain about 50 florets with five minute (1 mm long) petals, a single style, and five stamens with yellow anthers. The overall appearance is of a greenish-white fuzzy pincushion.

Desmanthus

Desmanthus illinoensis

Illinois bundleflower [Blooms: Jun-Aug]

Showy tick-trefoil flowers are about a 1/2" tall and 1" long, pea-like with five petals — an upper petal (banner or standard) with two elongate, yellowish-cream spots at its base, two lower petals (wings) forming a chamber perpendicular to the upper petal, and another pair of petals forming a "keel" within the wings. Emerging from between the wings and keel is a stout, upward-curved, white tube that bears a single style and several stamens at its tip.

Desmodium

Desmodium canadense

showy tick-trefoil [Blooms: Jun-Jul]

Pointed-leaf tick-trefoil flowers are a little over 1/4" long, pea-like, with four (or five) rose-pink petals — a banner (parallel to the other petals), two lateral wings, and a tube-like keel formed from either a single petal folded lengthwise or two fused petals (opinions differ). Emerging from between the wings and keel is a stout, upward-curved, white tube that bears a single style and several stamens at its tip.

Desmodium

Desmodium glutinosum

pointed-leaf tick-trefoil [Blooms: Jun-Sep]

Panicled tick-trefoil flowers have an upright banner (standard) with one or two patches of yellow-green near its base and two lateral wings that enclose the two petals that form the median keel; a robust column bearing the style and several stamens on its end pokes up through the keel and wings. The loments (seedpods) are covered in robust, hooked hairs, are 1/2-1.5" long, and have 2-6 rounded, incompletely separated segments; the segments are slightly convex on top and markedly angular-convex on the bottom.

Desmodium

Desmodium paniculatum

panicled tick-trefoil [Blooms: Aug]

Deptford pink flowers are 1/4-1/2" across with hairy petals that are pink with white dots, 10 stamens with purplish-pink anthers, and two 1 cm long, filamentous styles; the rounded tips of the petals are toothed. The calyx is long (3/4") relative to the size of the corolla, tubular, and hairy with five thin extensions; narrow bracts lie more or less parallel to the elongated calyx. No other local flower looks anything like Deptford pinks.

Dianthus

Dianthus armeria

Deptford pink [Blooms: Jun-Aug]

Sweet-William's (Dianthus barbatus) inflorescence, located at the apex of the stem, is a flat-topped or slightly domed cyme of 5-30 flowers. Individual flowers are about an inch across consisting of a tubular calyx about 3/8" long with five sharply triangular lobes; five broad, variously colored petals that have very narrow bases ("clawed") and a toothed or fringed outer edge; 10 stamens with purplish anthers (which often fall off the filament); and two styles. Fertilized flowers produce oval to cylindrical seed capsules about 1/2" long with four teeth around the open end. The flowers of Sweet-William are edible. Sweet-William prefers deep, organic-rich, well drained soils in full sun, preferably in a disturbed site. The sweet William plants growing in Jackson Park are undoubtedly escapees from a nearby garden (a rare event). The only other Dianthus spp. in Jackson Park is Deptford pink (Dianthus armeria), also a perennial exotic. The two species are similar in having fringed petals and a terminal inflorescence, but otherwise you would never confuse them; Deptford pink is a subtle beauty, sweet William shouts for joy.

Dianthus

Dianthus barbatus

sweet-William [Blooms: Jun-Jul]

The flowers of Dutchman's breeches are unmistakable — white (rarely pink) triangular flowers with two necter spurs angled laterally at 45° to the vertical (the "trouser" legs). Up to a dozen (usually 3-6) 3/4" flowers hang from flower stalks (a raceme) that arch over the leaves 4-8" tall; at the underside of the flowers are two yellow, wing-like lobes with the stamens and pistil emerging from between the lobes.

Dicentra

Dicentra cucullaria

Dutchman's breeches [Blooms: Apr-May]

Northern bush honeysuckle flowers occur in clusters of 2-7 arising from leaf axils or at the tips of year-old branches; the flowers are initially yellow but they turn orange-red with age. The flowers are funnel-shaped, 1/2-3/4" long, hairy on the inside, with four slender lobes and a fifth, wider and darker lobe; the base of the flower is surrounded by five triangular sepals as long as the floral tube. The five stamens are densely hairy with yellow anthers; the style is long, slender, green, with a dome-like stigma. The fruits are red, sac-like structures (the ovary) topped by the persistant sepals; the mature seed capsules are 1/3-1/2" long, green to brown in color, egg shaped or oblong (like medicinal capsule) filled with half-millimeter long, golden brown seeds.

Diervilla

Diervilla lonicera

northern bush honeysuckle [Blooms: May-Jul]

Annual wallrocket flowers occur on the tips of the stems. Each flower has four bright-yellow, oblong petals about 1/4" long with rounded tips; five light-green stamens with yellow anthers; and a green, stout pistil with an expanded, rough-textured stigma. The fruits are elongate (3/4-1"), narrow (1.5-2.5 mm), cylindrical siliques.

Diplotaxis

Diplotaxis muralis

annual wallrocket [Blooms: May-Oct]

Wild teasel produces one or more flowering stalks 2.5-6' tall, reddish- or pale green, with longitudinal ridges and scattered white prickles. The flowerhead is up to 4" tall and 1.5" across, initially egg-shaped but elongating as it matures. At the base of the flowerhead are narrow, prickly, sharply-pointed bracts up to 6" long that arch up to surround the flowerhead. Individual flowers are packed around the flowerhead like cells in a honeycomb, each flower with a 3/4" long bract that tapers to a sharp point. Individual flowers are white along most of their length, tubular, about 1/2" long, flaring out to four pale purple or lavender lobes; four stamens with white filaments and purple to lavender anthers and a single white style all protrude well beyond the end of the tube. Flowers bloom initially about halfway up the flowerhead but, later, rings of blooms develop at the base and apex of the flowerhead. Cut-leaved teasel was introduced to North America in the 18th century; the spiky flowerheads were used to comb wool and to raise the nap of (aka, "full") fabric. (Thus the species name, fullonum.) I've only seen this plant once in Jackson Park, but hope it returns (but not in excessive numbers).

Dipsacus

Dipsacus fullonum

wild teasel [Blooms: Jul-?]

Cut-leaved teasel behive-shaped flowerheads are 2-4" long and 1.5" across, spiky in every aspect. At the base of the flowerhead are 2-4" long, narrow bracts with sharp points that protrude radially. (These bracts in wild teasel, Dipsacus fullonum, arch up around the flowerhead.) Individual flowers are packed around the flowerhead like cells in a honeycomb, each flower with a 3/4" long bract that tapers to a sharp point. Individual flower are white, tubular, about 1/2" long, flaring out to four lobes; four stamens with white anthers protrude from the tube well beyond its end and there is a single style with a stigma positioned laterally at the style tip. Flowers bloom in a circle progressively from the base of the flowerhead to its tip.

Dipsacus

Dipsacus laciniatus

cut-leaved teasel [Blooms: Jul-Aug]

Flat-topped aster produces stems that are 2-5' tall and unbranched except at the inflorescence, a flat-topped cluster of small (1/2"-3/4") white flowers with few (2-15) broad but sparse ray florets ("petals"). The disc florets are initially yellow but become cream-colored with age. The branching of each stem produces a flat-topped panicle of flowerheads that is 3-12" across. Individual flowerheads are small (1/2-3/4" across) with 5-12 white ray florets around 12-25 yellow disc florets (but these may fade to a yellowish-tan color as the disc florets age). The base of each flowerhead is surrounded by appressed, oblong bracts ("phyllaries") in 2-4 layers ("series").

Doellingeria

Doellingeria umbellata

flat-topped aster [Blooms: Jul – Sep]

Whitlow-grass flowers are tiny (1/8" across) with four green or purplish, hairy sepals half as long as the petals, four white, deeply-cleft (bifid) petals, six stamens with yellow anthers, and a single green pistil. The fruit is a flattened, oblong seedpod, approximately twice as long as wide, <3/8" long, attached to the remnants of the flower pedicels; each seedpod contains ~40 seeds.

Draba

Draba verna

whitlow-grass [Blooms: Apr-May]

Prairie cinquefoil (aka, tall cinquefoil) flowers are about 3/4" across and have white to cream-colored petals, narrowest at the base; the sepals are light green and as long or longer than petals, tapering to a sharp tip; about 20 bright golden-yellow stamens and anthers; and the pistils in the center of the flower also bright golden-yellow. Prairie cinquefoil and sulfur cinquefoil are easy to confuse, but flowers of prairie cinquefoil are cream colored, not yellow and the leaves are pinnately compound, not and palmate.

Drymocallis

Drymocallis arguta

prairie cinquefoil [Blooms: Jun-Jul]

Mock strawberry (aka, Indian strawberry) flowers are borne on a single flower stalk. Flowers are 1/2-3/4" across with five sharply-pointed, triangular green sepals as long as the petals and covered with long hairs on their outer surfaces; five bright-yellow petals wider at the tip than the base; 15-25 stamens with bright yellow anthers; and a central yellow receptacle with numerous pistils covering its surface. Just below the sepals are five small bracts (leaves), each with three pointed lobes at its tip; these persist and are present below the sepals on the fruit. The fruit is a bright-red expanded receptacle ~1/2" in diameter, globose or ovoid, that is nestled in the sepals; bright red seeds project from the fruit's surface like pointed bumps. The fruit is edible but tasteless. The word "Indian" in the common name refers to the country "India" rather than Native Americans; "Indian" strawberry was introduced from Asia. The five small bracts (leaves) just below the sepals in mock strawberry, each with three pointed lobes at its tip, are present in both the flowers and the berries and are a diagnostic character of mock strawberry.

Duchesnea

Duchesnea indica

mock strawberry [Blooms: Apr-Sep]

Pale purple coneflower flowerheads sit alone at the top of the stem; there are 12-20 white to pinkish-purple, slender ray florets, with 2-3 notched teeth at the tips; the ray florets initially splay laterally but droop on maturity. The central disc is domed and covered with disc florets with reddish-purple tips.

Echinacea

Echinacea pallida

pale purple coneflower [Blooms: Jun-Jul]

Purple coneflower flowerheads are solitary, 2.5-4" across, on the end of light green stems with purple streaks. The center of flowerhead is a flattened or (usually) peaked cone of numerous reddish-orange disc florets about 1/4" long, tubular, deep red to purplish-brown in color; stamens bear yellow pollen. The 10-20 ray florets are each 1.5-3" long and 1/4-3/4" wide, initially spreading, but droop as they mature; they are pink to purple, elongate-oval, often with three notches at the tips of the petals.

Echinacea

Echinacea purpurea

purple coneflower [Blooms: Jul-Aug]

Yerba de tajo's flowerheads arise in groups of 1-3 from the leaf axils on short pedicels; individual flowerheads are 1/4-1/3" across with 8-16 triangular, green, basal bracts, numerous (20+) off-white, thin ray florets with a protruding style, and numerous (15+) light grey to cream disc florets with four tiny spreading lobes, and four protruding light brown anthers and a branching style. Ray flowers are pistillate; disc flowers have both stamens and pistils.

Eclipta

Eclipta prostrata

yerba de tajo [Blooms: Aug-Sep]

in common spike-rush, at the tip of the culm is a single spike, elongate-ovoid with a sharply pointed tip, up to about 1" long; 30-100 florets ( each with three stamens bearing dark yellow anthers and a split style) are spirally arranged around the spikelet, each protected by a pointed scale 3-5 mm long. The scales have a green to straw-colored midrib, reddish- or orange-brown flanks, and a translucent edge. The two lowest scales in the spike lack flowers. The lowest scale wraps less than 3/4 of the base; it is mostly green bordered by a brown band and a translucent, rounded edge and is more leathery than other scales.

Eleocharis

Eleocharis palustris

common spike-rush [Blooms: May-Jul]

Aunt Lucy (Ellisia nyctelea) flowers arise from the leaf axils. The flowers are small and tubular (1/4" wide x 1/2" long); the five petallike lobes are white with purple lines or specks; the five stamens are hidden within the corolla, alternating with the corollar lobes and the style is divided for about half ts length; the sepals are hairy and as large as the petals. The fruit is a 1/4" long hairy, white body that looks like two spheres squashed together, resting on the sepals; it usually contains 4 seeds. This species is very common in late spring in open but shaded areas on Wooded Island. How it acquired the moniker "Aunt Lucy" is obscure.

Ellisia

Ellisia nyctelea

Aunt Lucy [Blooms: Apr-Jun]

Cinnamon willowherb flowers are 1/4-1/3" across and arise from the axils of the upper leaves on 1/2" flower stalks, but the ovary of the flower is a hairy, elongate cylinder slightly wider than the flower stalk; the base of the sepals and petals (less than 1/4" long) may thus be elevated 1.5" above the leaf axil — a tiny flower on the tip of a long cylinder. Above the elongated ovary are four green sepals (with pink or purple tints), four deeply-notched white or light pink petals, a stout pistil with a knobby end, and eight stamens, four long, four short. After fertilization, the ovary elongates to as much as 3" long, dries to a brown color, then splits into two or four segments to release tiny seeds suspended under a tuft of long light brown hairs.

Epilobium

Epilobium coloratum

cinnamon willowherb [Blooms: Jul-Sep]

Broad-leaved helleborine's inflorescence is a 4-12" long raceme with 15-50 flowers, all on one side of the flower stalk. Individual flowers are 1/2-3/4" wide. The petals are greenish-purple with the lower petal forming a pale red bowl; behind the petals, the three sepals are pale green with purple stripes. (The sepals are as long as the petals, as are the bracts below the flowers' stalks.) The fruit is a hairy capsule ~1/2" long, and egg-shaped. Broad-leaved helleborine prefers woodlands.

Epipactis

Epipactis helleborine

broad-leaved helleborine [Blooms: Jul]

Annual fleabane flowers occur in clusters (panicles) in the upper parts of the plant, each 1/2-3/4" across. Disc florets are very small (2-3 mm) and golden yellow; the 50-120 ray florets appear very elongate (1/4-1/2") and narrow (~1-2 mm) and bright white in color. The back of the flower is covered with 2-4 rows of narrow, hairy bracts.

Erigeron

Erigeron annuus

annual fleabane [Blooms: May-Aug]

Philadelphia fleabane stems are usually unbranched except at the inflorescence, a panicle. Flowerheads are 1/2-3/4" across with 150-300 thin white ray florets, often pink or violet tipped, and densely packed around the 1/2" wide disc; the disc florets are yellow, tubular, and 5-10 mm long. The base of the flowerhead is coved by 1-3 series of light green, appressed phyllaries.

Erigeron

Erigeron philadelphicus

Philadelphia fleabane [Blooms: May-Sep]

In Robin's plantain the basal leaves, stem leaves, stems, and flower stalks are all very hairy. Flowerheads arise from the tips of the stems as a group of 1-6. Individual flowerheads are 1-1.5" across; the numerous (50-100) ray florets bear long white (sometimes light pink or violet) petals surrounding a flat, yellow-orange disc of disc florets ~1/2" across. The base of the flower is surrounded with 2-3 layers of light green phyllaries (often with brown or purple tips) which taper smoothy into the stalk.

Erigeron

Erigeron pulchellus

Robin's plantain [Blooms: Apr-May]

Daisy fleabane flowerheads are 1/2-3/4" across with 40-100 thin white or pink-tinged ray florets 4-7 mm long, usually shorter than the disc diameter and numerous yellow disc florets. The disc florets are tiny (1.5-2.5 mm), yellow, and tubular with five lobes on the apical end; there are five stamens and a single, bifurcated style. Around the base of the flowerhead are 2-4 rows of light green, 3 mm long phyllaries often covered with short hairs. Daisy fleabane is similar to Philadelphia fleabane (Erigeron philadelphicus), but the latter has larger flowers with more (150-300) ray florets and leaves that clasp the stems.

Erigeron

Erigeron strigosus

daisy fleabane [Blooms: Jun-Sep]

Storksbill flowers occur in clusters of 4-8. Each flower is 1/2" across with five hairy, green, widely-spreading sepals; five purplish or pink petals; five fertile stamens with reddish-orange anthers; and five fused pistils, separate at the tips of the styles where five purple stigmas in a star-shape are prominant. The fruit is a long, narrow awl-shaped "storksbill" up to 1.5" long whose base is the mature seeds (usually five) and whose long "bill" consists of the laterally joined awns (long bristle-like structures) of the seeds. The seeds are explosively dispersed when the "storksbill" splits longitudinally into five separate awns; the attached seeds are flung away from each other (at 4 meters/sec). The attached awns also allow each seed to self-bury. Storksbill is native to the Mediterranean; it was introduced to North America in the 18th century and is now naturalized.

Erodium

Erodium cicutarium

storksbill [Blooms: Apr-Jun]

Rattlesnake master inflorescences consist of whitish-green spiky balls 1/2-1" across made up of small florets enclosed by prickly bracts; the florets have five short, rounded petals, five stamens, and a long, divided white pistil that protrudes well beyond the edge of the floret. Note that, if you're bitten by a rattlesnake, this plant will be of no use to you whatsoever.

Eryngium

Eryngium yuccifolium

rattlesnake master [Jun-Sep]

Wormseed mustard stems are medium green, angular or grooved, covered relatively sparsely with tiny appressed hairs. At the tip of the stem is a raceme of yellow flowers, each 1/4-1" long and 1/4" across; more peripheral flowers in the raceme bloom first. Each flower has four pale green sepals 2-3 mm long, four yellow petals 3-5.5mm long, six stamens with yellow anthers (two stamens shorter than the other four), and a single style. The basal rosette withers about the time the seeds begin to form, while flowers are still present. Seedpods are four-angled siliques that grow directly from the center of the flowers. Wormseed mustard prefers open, disturbed habitats.

Erysimum

Erysimum cheiranthoides

wormseed mustard [Blooms: Apr-?]

Troutlily's reddish-brown flower stalk arises from the junction of the paired leaves; its tip (and consequently the single flower) is bent down at a 30-45° angle. Each flower is about 1.5" long but may be only 1/2" wide at night or early in the morning or over 1" wide later in the day as the petals spread. Each flower has six white tepals (three petals and three petal-like sepals), six stamens with large yellow anthers, and a single white style with a three-lobed stigma. The fruit is a three-chambered seed capsule about 3/4" long attached to the flower stalk which may nod when immature but the stalk straightens so the capsule is erect when mature.

Erythronium

Erythronium albidum

troutlily [Blooms: Apr-May]

Winged euonymous' younger stems and branches have geen bark and 2-4 cork-like "wings" (thin plates whose plane lies in a radius of the branch). Clusters of 1-3 flowers arise from leaf axils; individual flowers are about 1/3" (8 mm) across with four green sepals, four yellowish-green petals, four stamens, and a green central dome which bears the single pistil with a reddish, multilobed stigma. Four-lobed seed capsules become dark red or purple at maturity; they split to expose 1-4 reddish-orange arils.

Euonymus

Euonymus alatus

winged Euonymus [Blooms: May-Jun]

Eastern wahoo (Euonymus atropurpureus) is a native shrub or small tree whose range covers most of the eastern half of the U.S. The inflorescence is a branching cyme that arises from a leaf axil; the cyme carries seven to about twenty reddish-purple to maroon flowers. Individual flowers are about 8 mm (a bit over 1/4") across, hairless, with four greenish purple, oval sepals that are fused at their bases; four spreading, reddish purple, oval petals; four stubby stamens with yellow anthers; and a pistil with a short, stout, green style. Fertilized flowers produce a four lobed seed capsule, initially light pink or pale purple but maturing to pinkish purple. The seed capsule splits open in the fall to expose four fleshy, bright red arils (the fruits), each of which contains two seeds. A handout occasionally distributed by the Jackson Park Advisory Council ("Wooded Island Tree Identification") identifies one tree on the west side of Wooded Island (south of Osaka Garden) as an Eastern Wahoo. This tree, unfortunately, is not an Eastern wahoo but is instead an exotic species of Euonymus — a European spindletree (E. europaeus). Indeed, all the Euonymus sp. on Wooded Island are one of three exotic species — winged Euonymus (E. alatus), European spindletree (E. europaeus), or Hamilton's spindletree (E. hamiltonianus) and all three have blooms that lack the deep maroon color of Eastern wahoo's flowers. A sapling labeled "Eastern Wahoo (Euonymous atropurpureus)" was planted on the south shore of Columbia Basin in 2022. When it bloomed this year (2026) and showed maroon petals on the flowers, I could finally confirm that species identification. The seed capsule of Eastern Wahoo is pinker than those of European spindletree (E. europaeus) or Hamilton's spindletree (E. hamiltonianus) and the arils are orange or scarlet respectively, not the red of Eastern wahoo. The best way to distinguish the three species is by the color of their petals — only Eastern wahoo has reddish purple to maroon petals, while the other two species have petals that are white, green, or yellow.

Euonymus

Euonymus atropurpureus

Eastern wahoo [Blooms: Jun]

European spindletree flowers (usually less than 7) occur in clusters (cymes) with long peduncles; they have four sepals, four petals, four stamens with white anthers, and a single stout style. The greenish-white or yellow petals on the flowers appear to be very narrow, half the width of the petals of Hamilton's spindletree. (In reality, the petals are curled into a U-shape towards the stem so they only appear narrow.) The sepals are pale green, about half the length of the petals, and bent back beneath the flower. The fruit is pink, not red; the arils covering the seeds are orange, not red or scarlet. European spindletree blooms later in the spring in Jackson Park than Hamilton's spindletree.

Euonymus

Euonymus europaeus

European spindletree [Blooms: Apr-Jun]

Hamilton's spindletree produces clusters of about seven flowers on ~1.5" peduncles that grow out of the leaf axils. Individual flowers are <1/2" across with four white, elongate-oval petals with rounded tips, four stamens with dark purple (approaching black) anthers, and a large green ovary with a single, stout green style. The fruit is a four chambered, deeply-grooved, rose-colored capsule ~1/2" across containing four scarlet, fleshy arils, each surrounding an ellipsoidal, dark brown seed.

Euonymus

Euonymus hamiltonianus

Hamilton's spindletree [Blooms: Maay-Jun]

Tall boneset flowerheads are tiny (1/8" across) with no ray florets and typically only five disc florets. Disc florets are dull white with a tubular corolla and a long bifurcated style that extends well away from the floret; the base of the style is greenish and surrounded by five brown stamens with white tips. The apex of the corolla has five prominant, triangular lobes that give the florets a star-like appearance.

Eupatorium

Eupatorium altissimum

tall boneset [Blooms: Aug-Oct]

Common boneset's upper stem and branches bear clusters 2-8" across of white flowerheads. Each flowerhead is about 4-6 mm across consisting of ~15-20 dull white disk florets (ray florets are absent); florets have a tubular corolla with five triangular lobes at the apical end and a long, bifurcated style surrounded at its base with a brown column of five stamens with purplish anthers. Ironically, "common" boneset is less common than late boneset or tall boneset in Jackson Park.

Eupatorium

Eupatorium perfoliatum

common boneset [Blooms: Jul-Aug]

Late boneset's inflorescence is a flat-topped or shallowly-domed panicle with numerous flowerheads. Individual flowerheads are composed of 12-15 greyish-white disk floret (ray florets are absent) about 1/4" long with a tubular corolla with five small, triangular apical lobes and a long white bifurcated style extending well out from the floret surrounded by five black stamens. Leaf venation, lack of leaf hairs, and and smaller flowerheads (~5-8 florets) distinguish tall bonset (E.altissium) from late boneset (E. serotinum; 12-15 florets).

Eupatorium

Eupatorium serotinum

late boneset [Blooms: Aug-Oct]

Flowering spurge "flowers" are deployed in an open, flat-topped inflorescence (panicle); individual "flowers" are 1/4-3/8" across, a cup-like, five-lobed cyathium (unique to euphorbs) containing the five white "petals" (actually white bracts), a green ring of nectar glands around the base of the "petals," and the stamens or styles. Male flowering spurge cyathia have three stamens, each with a white filament and a yellow anther; female flowering spurge cyathia have both an ovary with a tripartite style with six stigmas, and three (sterile?) stamens. (If you're confused about the architecture of cyathia, see seaside sandmat (Euphorbia polygonifolia) for a clearer example.) After fertilization, the fruit develops as a unmistakable three-celled, bulbous green capsule on a short stalk in the middle of the original flower with the remnants of the style at its tip.

Euphorbia

Euphorbia corollata

flowering spurge [Blooms: Jun-Oct]

Seaside sandmat cyathia (cup-like reproductive structures typical of euphorbs) develop between pairs of leaves, typically one cyathium with a short reddish stalk per pair of leaves. On the rim of the cyathium are four to six red nectar glands; each nectar gland alternates with a narrow, elongate lobe. In the center of the cyathium is a female flower with a three-lobed, light green ovary topped by a tripartite style; the flower sits on a stout pedicel that elongates and curves as it matures. Between the central female flower and the rim of the cyathium are several male flowers, each consisting of a single stamen. Seaside sandmat prefers beach habitats around the Great Lakes and along the Atlantic coast.

Euphorbia

Euphorbia polygonifolia

seaside sandmat [Blooms: Jul-Sep]

Lance-leafed goldenrod is only distantly related to the other goldenrods (all genus Solidago) found in Jackson Park. The inflorescence is a flat-topped or slightly domed panicle. Flowerheads are cylindrical, minute (1/8" across, the smallest of the goldenrods), with 15-25 ray florets with minute petals and 5-10 disc florets. The outermost bracts around the base of the flower are green-tipped. Flowers across the inflorescence bloom at different times so the inflorescence often looks a bit shopworn. Lance-leafed goldenrod refers wet, soggy habitats.

Euthamia

Euthamia graminifolia

lance-leafed goldenrod [Blooms: Jul-Sep]

Spotted Joe-Pye weed flowerheads are pink to pinkish-purple, about 8 mm long, consisting of 8-20 disk florets, each with a tubular corolla with five tiny spreading lobes at its apex, five stamens with white anthers, and two long, thin white styles that extend well outside the floret; there are no ray florets. The flowers make either a rather flat or domed cluster (panicle) at the apex of the plant. The bracts (phyllaries) around the base of the flower are purple-tinged or the same color as the disc florets. Spotted Joe Pye weed (E. maculatum) has purple or purple-spotted, hairy stems and flowers with 8-20 disc florets; sweet Joe Pye weed (E. purpureum) has green, hairless stems with purple color only at the leaf nodes and flowers with 4-7 disc florets.

Eutrochium

Eutrochium maculatum

spotted Joe-Pye weed [Blooms: Jun-Sep]

Sweet Joe-Pye weed's inflorescence is a domed or pyramidal panicle. The flowerheads are whitish-pink to pinkish-purple and strikingly variable in color between plants, 1/4-3/8" long, consisting of 4-7 disk florets, each with a whitish-pink to purplish-pink tubular corolla with five lobes at its apex, two long, thin white styles extending well outside the floret and five stamens fused to the corolla about halfway up its length; there are no ray florets. The flowerheads make a domed (rather than flat) cluster at the apex of the plant. The bracts (phyllaries) around the base of the flowerhead are pale pink.

Eutrochium

Eutrochium purpureum

sweet Joe-Pye weed [Blooms: Jul-Aug]

Black bindweed flowers develop in singletons or pairs from the leaf axils or directly from the stem. Flowers are 1/8-1/4" long; they have 3-5 greenish-white, white, or light purple petal-like tepals, the outer three tepals with a ridge or keel down the midline on the outer surface. Six to eight stamens with purple anthers surround fused green styles with a dome-shaped stigma in the middle of the flower; the flower usually opens only partially (like a tulip). The fruit is three-sided, with a tubercle-covered surface, about 1/4" long, black when fully mature. Black bindweed is very similar to climbing false buckwheat (Fallopia scandens).

Fallopia

Fallopia convolvulus

black bindweed [Blooms: Jun-Jul]

Climbing false-buckwheat stems are round, angular, or ridged in section, often with hairs on the ridges. Racemes of flowers arise from the leaf axils; the flower stalks are usually vertical, 3-8" long and bear both erect flowers and drooping fruits. Individual flowers are greenish-white, about 3/16" across have eight stamens with white anthers and an ovary bearing a tripartite style; the thee outermost tepals (petals) have obvious wings, unsually with an undulating margin; the inner two tepals are simple ovals. The fruit (~3/8" long) has a greenish center with three white wings; the 3 outer tepals with enlarged wings enclose the seed. (The fruit resembles a much-enlarged version of the fruit of curly dock (Rumex crispus).) Climbing false-buckwheat is very similar to black bindweed (Fallopia convolvulus) but is far more common in Jackson Park.

Fallopia

Fallopia scandens

climbing false-buckwheat [Blooms: Aug-Sep]

Queen-of-the-prairie produces over 100 flowers (1/3" wide) in the panicle with five triangular, purplish sepals, five rounded pink petals with narrow bases, 15+ long white stamens with pink anthers, and a ring of 5-15 curved styles with large, disk-like, white stigma. The fruits are striaght or slightly curved stout banana-like spindles 1/4-1/2" in diamater on a narrow stalk.The numerous pink flowers with their long protruding stamens tipped with pink anthers gives the inflorescence the air of pink clouds, or possibly cotton candy. Rare, but unmistakeable if you spot it. Critically imperiled in Illinois (and elsewhere in the Midwest).

Filipendula

Filipendula rubra

queen-of-the-prairie [Blooms: Jul-Aug]

Forsythia flowers occur singly or in clusters of 2-3 arising from the axils of leaf buds; the flowers have short (1/8-1/4") pedicels. The flowers consist of four green 1/4" long sepals fused at their bases; a bell to saucer-shaped corolla that also has four deep, strap-shaped, brilliant yellow lobes; two stamens that are fused to the base of the corolla tube; and a single style with a pair of ascending, hemispherical terminal lobes (the stigmas). Forsythia is distylous, producing either short (3-5 mm) stamens in combination with long (5-7 mm) pistils or long (6-7 mm) stamens in combination with short (3 mm) pistils. Each of these flower morphs is restricted to a given plant; forsythia is an obligate outcrossing species. Fruits are rarely produced in North American forsythia, possibly because the complementary flower morph is rarely in close proximity to a given plant. However, forsythia can propagate asexually via cuttings.

Forsythia

Forsythia suspensa

forsythia [Blooms: Mar-Apr]

Wild strawberry always show a terminal marginal tooth of each leaflet that is shorter (and often narrower) than the teeth on either side, a diagnostic character. Clusters of white flowers are borne on 5" long, hairy peduncles. Individual flowers are on 3/4" long (again hairy) pedicels. The flowers are 1/2-3/4" across; there are five green, narrow, pointed, hairy sepal-like bracts; five hairy, lance-shaped sepals; five oval white petals longer than either the bracts or the sepals; and variable reproductive organs depending on whether the flower is male (least common, with ~20 yellow stamens and anthers), female (with a central yellow dome of pistils), or "perfect" (both male and female, with the appropriate organs). Fruits are familiar, if small (1/2") strawberries, bright red when ripe, with the seeds sequestered in sunken pits so the surface is mostly smooth; the fruit hangs beneath - and is tightly embraced by - the sepals and sepal-like bracts, is edible, and is tasty, if a bit tart. Wild strawberry superficially resembles mock (Indian) strawberry in its foliage and (superficially) fruit, but wild strawberry has white flowers, not yellow; the fruit of wid strawberry hangs below the sepals rather than resting above the sepals as in mock strawberry; and the seeds of wild strawberry lie embedded in the surface of the fruit rather than protruding as in mock strawberry.

Fragaria

Fragaria virginiana

wild strawberry [Blooms: Apr-May]

Green ash is dioecius; each tree produces only either male (staminate) or female (pistillate) flowers (which are wind pollinated). The flowers open in mid-spring, before the leaves emerge. Male flowers are produced in compact clusters that envelop short sections of the second-year twigs. Each staminate flower is yellowish green to greenish purple and less than 1/8" (3 mm) across, consisting of a tiny, four-lobed, tubular calyx and a pair of purplish stamens. Petals are absent. Female flowers are also produced on the second-year twigs, in this case in small panicles. Each female flower consists of a tiny four-lobed, tubular calyx and a pistil with a single, long style; again, petals are absent. Fertilized flowers are replaced by panicles of drooping, spatula-shaped, winged seeds 1-2.5" long and 1/4-1/3" wide that have an ellipsoid swelling at one end containing the seed and a single elongated, membranous wing with a rounded or notched tip. When released in the autumn, the greenish to tan fruits spin around the seed, reducing their rate of fall so they can be carried greater distances by the ambient wind. Green ash is tolerant of shading so can grow in mature forests; it prefers moist soils and can tolerate some flooding.

Fraxinus

Fraxinus pennsylvanica

green ash [Blooms: May?]

Indian blanket flowers are 1-2.5" across with 6-15 sterile ray florets; the petals are 3/4-1.25" long, red or brownish-red with yellow tips; the base of the petal is narrow and the tips of the petals are divided into three sharp or rounded teeth or lobes. Disc florets are brown, numerous (40-100+), with tubular corollas that may be orangish, red, brownish-red, or purple with five tringular, hairy lobes at the apex; the flowers are perfect with both stamens and styles.

Gaillardia

Gaillardia pulchella

Indian blanket [Blooms: Jul-Oct]

The white, waxy, drooping flowers of greater snowdrop are born on leafless scapes (flower stems). The flowers consist of three white outer tepals and three white inner tepals; the outer tepals have distinctly narrowed bases while the inner tepals are more rectangular, usually with a green blotch at their base and tip or a bold green stripe running from base to tip. (Common snowdrop flowers have a single, restricted blotch of green on their inner tepals.) There are six stamens with yellow anthers recessed inside the edge of the inner tepals; the stamens form a ring around the style. The style is slender, cylindrical, and slightly longer than the stamens. The fruit is a spherical to ellipsoid green capsule that splits into thirds when ripe, releasing the seeds.

Galanthus

Galanthus elwesii

greater snowdrop [Blooms: Mar-Apr]

Snowdrop is the earliest blooming flower in Jackson Park (late February); individual blooms can persist for about a month. The bell-shaped flowers hang down on a thin peduncle from a smooth, hairless flower stalk up to 10" long. The flowers have six oval, half-spread tepals; the three outer tepals are white with rounded tips, the three inner tepals are white with green, notched tips and green stripes on the interior surface. There are six stamens with yellow-orange anthers and a single greenish-white style. The fruit is a green, egg-shaped enlarged ovary with a flattened distal tip that dangles form the peduncle. Snowdrops usually exist in a given spot because of a prior deliberate cultivation (in some recorded cases, up to 60 years earlier) and rarely pose an invasion threat; they typically propagate from bulbs. The source of the snowdrops in Jackson Park is unknown.

Galanthus

Galanthus nivalis

snowdrop [Blooms: Feb-Mar]

Gallant-soldier (aka, small-flowered galinsoga) flowerheads are about 1/4" across; they have 4-8 (usually 5) ray florets with a single minute (about 2x2 mm) white petal notched to produce two or three lobes; the ray florets are distributed around the circumstance of the disc. There are 15-50 golden yellow, tubular disc florets with five short triangular lobes at their apex. Both ray and disc florets are fertile; the ray florets are pistillate while the disc florets are perfect (both pistils and stamens). The fruit (a cypsela) consists of a black, conical seed suspended beneath about five off-white, papery, fringed scales that act as a parachute. Gallant-soldier is very similar to galinsoga (Galinsoga quadriradiata); the latter has larger flowerheads and ray floret petals.

Galinsoga

Galinsoga parviflora

gallant-soldier [Blooms: Aug-Sep]

Galinsoga (aka, Peruvian daisy or shaggy soldier) flowerheads are small (1/4" across) with 4-8 (usually five) widely separated 2.5 mm long, white ray florets with three teeth at their tips. The 15-35 disc florets are yellow. Both ray and disc florets are fertile; the ray florets are pistillate while the disc florets are perfect (both pistils and stamens). The fruit (a cypsela) consists of a black, conical seed suspended beneath about five off-white, papery, fringed scales that act as a parachute. A poisonous plant (Tridax procumbens) with nearly identical flowers (but distinctly different leaves) is (luckily) restricted to FL and TX in the U.S. so not likely to show up in Jackson Park. The name Galinsoga ciliata, sometimes still used for Galinsoga quadriradiata, is invalid (ITIS); according to the USDA Plants database, C. ciliata has been superceded by either G. quadriradiata or G. urticifolia.

Galinsoga

Galinsoga quadriradiata

galinsoga [Blooms: Jun-Oct]

Cleavers' flowers are tiny (2-3 mm across), star-shaped, with two green carpels covered with hooked hairs joined at the base of the flower; four white, pointed petals; four stamens; and two styles. The fruit is a spherical capsule formed from the carpels, covered with stiff, hooked hairs, each carpel containing a single seed.

Galium

Galium aparine

cleavers [Blooms: Apr/May-?]

Dyer's greenweed is a woody shrub that grows 2-3' tall, introduced from Europe and Siberia (and probably escaped from gardens). The multiple stems are green and round in section. The leaves are 1/2-1" long and about half as wide, alternate, sessile, lance-shaped or oblong, hairy on the upper surface, with smooth margins. The inflorescence is a 1-3" wide raceme. Individual flowers are 1/2-3/4" across, bright yellow, with a strong resemblance to tick-trefoils — a banner held at about a 45° angle, two wings and two parallel keels. The fruit is a 1-3" long pea-like pod containing 8-12 black, shiny seeds. The common name derives from the use of this plant to produce a yellow dye.

Genista

Genista tinctoria

dyer's greenweed [Blooms: Oct]

Cream gentian the leaves are olive-green, lance-shaped with a pronounced fold along the midvein, 3" long and 2" across, and clasp the stem. Although most leaves are opposite (in pairs), the leaves just below the flowers occur in a whorl of three. The flowers are mostly apical, some version of white or cream, tubular, with the petal's veins outlined in green, about 1-2" tall and 3/4" across, and oriented near-vertically. The five petals remain tightly appressed, with only a small opening where their apices meet; the five stamens and pistil with a bifurcated stigma are usually hidden from view. Bumblebees are the primary pollinators.

Gentiana

Gentiana alba

cream gentian [Blooms: Jul-Oct]

Carolina crane's-bill flowers are small (about 1/4-3/8" across), in small clusters on stubby pedicels. Each flower contains five dull-green, very hairy, lance-shaped sepals with long, scarlet-tipped awns on the tips, five white to pinkish-lavendar petals shorter than the sepals, ten stamens with tan anthers, and five stamens fused at their bases. The fruit is spherical with a very long beak divided longitudinally into five sections; when ripe (the fruit turns bright red) , the beak splits violently into five strips attached to each other at their distal ends, flinging the seeds far from the parent plant. Carolina crane's-bill has white to pinkish flowers with sepals longer than the petals; cut-leaved crane's-bill (Geranium dissectum) has deep pink to purple flowers with sepals the same length as the petals.

Geranium

Geranium carolinianum

Carolina crane's-bill [Blooms: May-Jun]

Cut-leaved crane's-bill's very attractive flowers occur in pairs. The base of the flower is covered by five green sepals the same length as the petals, covered externally in glandular hairs; the tips of the sepals are drawn out into a short (1-2 mm) awn that is scarlet-tipped. The five petals are a deep pink to purple in color; there are five pink stamens with purplish-yellow anthers; the five styles produce a deep pink, star-shaped stigma at their tips. The fruit consists of five hairy spheres around the base of an elongate "crane's bill" which splits explosively when ripe into five strips attached at their distal ends, flinging the seeds far and wide. Carolina crane's-bill (Geranium carolinianum) has white to pinkish flowers with sepals longer than the petals; cut-leaved crane's-bill has deep pink to purple flowers with sepals the same length as the petals.

Geranium

Geranium dissectum

cut-leaved crane's-bill [Blooms: May-Jun]

Wild geranium flowers are about 1.5 " across; they have five spindle-shaped, green sepals with a short red-tipped awn at their tips and five purplish-pink petals, twice the length of the sepals, that are egg-shaped with broady rounded tips and have darker fine radiating lines that function as necter guides. The ten stamens have pale yellow anthers; the single pistel has five carpels that splay at the tip of the pistil into a starfish shape. The anthers produce pollen while the five styles' stigmas remain pressed together; after the anthers are spent, the stigmas separate. The fruit is a candle-shaped, cylindrical structure with a sharp tip. The carpels build up tension as they dry until they spontaneously snap near their base (above the sepals); as the carpel violently curls upward, it flings a single seed considerable distances like a tiny catapult.

Geranium

Geranium maculatum

wild geranium [Blooms: Apr-Jun]

White avens blooms slightly later than rough avens (Geum laciniatum); it reaches about the same size (1.5-2.5' tall). The flowers are 1/2" diameter; they have five green sepals that are white-edged, pointed, and the same length or (usually) shorter than the petals; five white, rounded petals with a narrow attachment; and numerous (25-120) stamens surrounding a dome-shaped mass of green styles about a third the diameter of flower. The sepals initially lie under the petals but later become reflexed back parallel to the flower peduncle.The spherical fruit is covered with long, hooked spines (actually, persistant styles) that help the seeds stick to fur and clothing. White avens is distinguished from rough avens (G. lacinatum) by their flower stalks covered with short, fine hairs (rather than long, coarse hairs) and sepals that are shorter than the petals.

Geum

Geum canadense

white avens [Blooms: Jun-Jul]

Rough avens flowers are 1/2" wide, with five triangular green sepals longer than the petals, five cream or white, circular petals with narrow attachments, and numerous (25-120) stamens with (initially) cream-colored anthers distributed around a central gumdrop-shaped mound of green carpels with long styles. The fruit is more or less spheroid, 3/4" across, and covered with long, hooked spines (actually, persistant styles) that help the seeds attach to clothing and animal fur. Note that some sources identify this species as Geum virginianum, but G. virginianum is the cream avens according to the USDA Plants database; Hilty (ILW) lists G. virginianum as "restricted to southern Illinois". The two species are very similar, but G. lacinatum has very hairy stems and hairless receptacles and G. virginianum has smaller flowers (1/3") with cream-colored petals dwarfed by the sepals. Rough avens is distinguished from white avens (G. canadense, also found in Jackson Park) by petals that are shorter than the sepals and their very hairy flower stalks; rough avens also blooms earlier than whte avens.

Geum

Geum laciniatum

rough avens [Blooms: June]

Prairie smoke leaves, stems, and the exterior of the flowers are densely hairy. Reddish-green or -purple flowering stalks arise from the center of the leaf rosette; they produce three buds at their apex which develop into three nodding flowers (as implied by the species name) with a pair of bracts at the base of the triplet that are divided into narrow strips as if cut with scissors. Each flower is 3/4-1" in both dimensions; five triangular red to reddish-purple sepals hide almost all the remainder of the flower, covering all of the five white or reddish petals except their tips, a ring of stamens, and a central cluster of pistils. The opening to the interior of the flower is highly constricted. A spreading, narrow floral bract identical in color to the sepals lies between each pair of sepals (for a total of five). After fertilization (by bumblebees), the flower peduncle straightens so the flower points straight up. A dense cluster of seeds attached to 2" long, feathery plumes (the "smoke") transform the appearance of the flower; the seeds are later dispersed by the wind. Frustrated bumblebees unable to force their way into flowers (and some wasps and beetles) may occasionally chew their way through the sepals and petals near the base of the flower to access the nectar. No other avens (Geum sp.) in Illinois produces seeds with feathery plumes; prairie smoke's closest relatives in Jackson Park, whte avens and rough avens, look nothing like it.

Geum

Geum triflorum

prairie smoke [Blooms: Apr-Jun]

Ground ivy flowers are 1/2" long and arise from the leaf axils; they are purplish, trumpet shaped, with a notched upper and lower (the largest) lobe and two small side lobes; the "throat" of the lower lobe is hairy. There are four stamens (two long, two short) with purple to blue anthers, and a single pistil with a bifurcated purple style. The corolla of the flowers is cupped by a hairy, green, tubular calyx that has 15 ridges distributed around the calyx running longitudinally, and five triangular teeth at the apex of the calyx. The fruit is a nutlet that nestles in the calyx.

Glechoma

Glechoma hederacea

ground ivy [Blooms: Apr-May]

Honey locust is a native tree that grows 50-100' tall; it has a single trunk 2-3.5' in diamater. The bark on the trunk is gray-black, divided into plates with peeling edges; the bark of twigs and branches is smoother, brown, and hairless. New shoots are green and fuzzy. Leaves are alternate and invariably compound, either even-pinnate (i.e., the leaflets are all paired, with no terminal leaflet) all 6-14" long with 5-11 pairs of leaflets, or bipinnate (i.e., the primary divisions of the compound leaf are themselves pinnate) with 4-7 pairs of even-pinnate leaflets 6-14" long, each with 5-11 pairs of leaflets. Leaflets are 3/4-1.5" long and about a third as wide. Thorns, both simple and branched, are usually present, especially on the trunk, but a thornless form exists; newly formed thorns can be a brilliant red. Flowers are present in 2-5" long racemes, usually as either male or female, but perfect flowers may be present. The flowers are small (1/8-1/4" across) and greenish-yellow. The fruit is a 6-14" long, dark-brown seedpod.

Gleditsia

Gleditsia triacanthos

honey locust [Blooms: May-Jun]

Kentucky coffeetree produces a single 1.5-3' diameter trunk that, with its branches, can reach heights of 60-90'. The trunk bark is rough, scaly, gray or gray-brown; the bark on the branches is smoother, gray; the bark on the twigs is gray or brown with whitish lenticels. The leaves are alternate, bipinnate-compound, with 5-9 pairs of pinnate leaflets, each with 6-14 pairs of subleaflets. The entire compound leaf can be 3' long and 2' across, the largest leaf of any native tree in Illinois. Individual trees may produce only male flowers, only female flowers, or "perfect" flowers with both male and female organs flowers; the flowers develop as racemes on terminal branches fairly high in the crown shortly after the tree leafs out in the spring. Flowers are about 3/4" long and 1/2-5/8" across with a narrow, tubular calyx bearing five thick, narrow, sepals, and five narrow, greenish-white petals, slightly wider than the sepals, and a central column about as long as the petals that contains the reproductive organs. The male and perfect flowers have 10 fertile stamens (in alternating long/short pairs) in the central column; the female and perfect flowers have a fertile ovary and a single style contained in the central column. The calyx, sepals, and petals are all densely wooly with short hairs. The fruit is a stubby, reddish-brown seedpod 3-6" long and 1.5-2" across, somewhat flattened but less so than the fruits of honey or black locust. The seeds are brown, VERY hard, oval, and about a half inch long and across; they are toxic when raw but can be eaten after roasting.

Gymnocladus

Gymnocladus dioicus

Kentucky coffeetree [Blooms: May-Jun]

Although stickseed flowers are tiny (1/8"), they have the ususal complement of parts — a hairy green calyx with five long, narrow teeth that alternate with the petals; five rounded white (or light blue) petals (actually lobes of the corolla tube); five arching, scale-like structures surrounding the opening to the tube; five stamens largely hidden inside the corolla tube; and a four-lobed ovary with a short style, similarly hidden inside the corolla tube. The fruits are globular, <1/4" across, densely covered with hooked prickles; they are purportedly the most difficult of such "sticktights" to remove from clothing.

Hackelia

Hackelia virginiana

stickseed [Blooms: Jul-Aug]

Sneezeweed flowers (1-2" across) have a more or less hemispherical central disc of 200-400 yellow-orange disc florets (which have both pistils and stamens) are each less than 1/8" across, surrounded by 10-15 pistillate ray florets that are triangular (narrowest at the insertion on the central disc) and three- or four-lobed along the squared-off distal margin ("doubly-notched"). The domed central disc on the flowers and the winged stems are diagnostic for this species. The base of sneezeweeds' flowers are covered by a single layer of long, narrow bracts that are fused together at their bases. Sneezeweed flowers are very similar to bitterweed (Helenium amarum) but the latter has long, thread-like leaves; I've not seen bitterweed in Jackson Park. The foliage contains sesquiterpene lactones that are bitter and toxic to mammalian herbivores, including cattle and sheep. The name "sneezeweed" may actually come from observation of Native American's use of snuff made from this plant.

Helenium

Helenium autumnale

sneezeweed [Blooms: Aug-Oct]

Woodland sunflower flower stalks tend to be hairier than the stem. The flowerheads are 1.5-3" across with 8-15 ray florets with yellow petals (with a tiny notch at the tip) and over 40 yellow, tubular disc florets with five spreading apical lobes. Flower bracts cup the back of the flowerhead in four series, light green, pointed, hairy along their margins, and typically recurved. Only the disc florets are fertile; the ray florets are sterile. Woodland sunflowers can be recognized by their nearly-sessile or sessile, opposite, leaves and broad leaf bases.

Helianthus

Helianthus divaricatus

woodland sunflower [Blooms: Jul-Oct]

Sawtooth sunflower flowerheads are 2.5-4" across with 10-20 bright yellow ray florets and over 100 tubular golden-yellow disc florets with five protruding brown anthers fused around a yellow style with a bifurcated stigma. Behind the flowers are multiple layers of spreading bracts that are pointed with hairy margins, especially near their base. Only the disc florets are fertile; the ray florets are sterile. (This is true throughout the genus Helianthus, although this situation seems more understandable (to me) than the the situation in the genus Silphium, where the opposite is true.) Sawtooth sunflowers can be distinguished from other Helianthus spp. by their hairless, reddish-purple stems; the arching leaves with a longitudinal fold are also characteristic but not definitive.

Helianthus

Helianthus grosseserratus

sawtooth sunflower [Blooms: Jul-Sep]

Downy sunflower is a very attractive sunflower which blooms in late summer. The composite flowers arise directly from the main stem. Each flowerhead is 2-4" across with 15-30 yellow ray florets and over 75 yellow disc florets in a 1" diameter central disk. Individual ray florets are sterile, the "petal" is about 1-1.5" long. Disc florets are about 1/4" long with five triangular lobes at the end of a tubular corolla; five stamens with white filaments (fused around the base of the style) and purple-brown anthers; and a single style, bifurcated at its tip, which protrudes above the stamens.

Helianthus

Helianthus mollis

downy sunflower [Blooms: Aug-Sep]

Western sunflower is a spindly plant that leads a double life. It is a perennial that first produces a very large (1.5' across) basal rosette of leaves; that basal rosette in turn produces a 2-4' tall, nearly leafless, stem. Clusters (a panicle) of 1-4+ flowerheads are present on pedicels less than 6" long emerging from the stem or upper leaf axils. The flowerheads are 1.5-2.5" across, with 8-20 ray florets, each bearing oblong yellow petals, and over 50 tubular, yellow disc florets with five lobes on their tips and five protruding brown anthers fused around a yellow style with a bifurcated stigma. Only the disc florets are fertile; the ray florets are sterile. (True throughout the genus Helianthus, although that seems more understandable (to me) than the situation in the genus Silphium, where the opposite is true.) Behind the flowerhead are 20-25 lance-shaped bracts (phyllaries) 5-7 mm long with pointed, green or straw-colored tips; there are often hairs round the margins of the phyllaries. The long, sparsely-leaved stem is diagnostic.

Helianthus

Helianthus occidentalis

western sunflower [Blooms: Aug-Sep]

Jerusalem artichoke should rightly be called a "sunflower" like the other four members of the genus Helianthus present in Jackson Park. Five to fifteen flowerheads ride on hairy peduncles up to 8" long and are 2.5-3.5" across; each is cupped by 2-3 overlapping series of phyllaries (bracts) that are more triangular than lance-shaped, hairy, and sharply pointed. The flowerheads consist of 10-20 sterile, yellow ray florets; the 60+ fertile disc florets consist of tubular yellow corollas about 1/4" long with five lobes at their apex and five protruding brown or black anthers fused around a yellow style with a bifurcated stigma. Jerusalem artichoke was cultivated by the indigenous peoples of the midwest for its tasty and carbohydrate-rich tubers.

Helianthus

Helianthus tuberosus

Jerusalem artichoke [Blooms: Aug – Oct]

Ox-eye sunflower (aka, false sunflower) flowerheads are 1.5-3.5" across with a prominant, gumdrop-shaped central disk; the plane of the flowerhead is horizontal, not vertical like most other (true) sunflowers. The 1.5-3" wide flowerheads consist of 10-18 yellow, tubular ray florets with yellow to golden-yellow, elongate-oval petals with notched tips and with two longitudinal folds in each petal; the numerous (10 to over 75) disc florets are yellow, tubular with five (brighter) yellow spreading apical lobes on the tubular corolla. Both disk florets and ray florets have a protruding, bifurcated style; the disc florets also have five stamens with brownish anthers which encircle the style below the paired stigmas. Behind the flower are two series of hairy bracts, the outer layer longer than the inner (a diagnostic character) and a velvety pedicel 1-8" long. Ox-eye sunflower is a "false sunflower" because both the ray and disc florets are fertile and can produce seeds; in true sunflowers, only the disc florets produce seed. The posture of the flower (horizontal rather than nodding towards the vertical) is also distinctive.

Heliopsis

Heliopsis helianthoides

ox-eye sunflower [Blooms: May-Jul]

Day lily stems/flower stalks are 3-6' tall and hairless; 5-9 flowers arise on a small panicle. The flowers are erect, orange with a yellowish center but without spots, large (3-4" wide), with six tepals (petals and similar sepals) with a white medial line and tips that curl backwards. The margins of the tepals are rolled inwards. The flowers have a single straight style and six stamens that curve markedly upwards. The flowers last only a single day. (Thus, the common name.) The seedpods are six-lobed, egg-shaped, and internally divided into three compartments, but the black seeds are inviable; day lilies are a sterile triploid hybrid that has escaped cultivation and reproduces only vegetatively. Day lily is considered invasive and spreads easily. The flowers can be cooked and eaten like squash blossoms and the leaves and tubers are edible when young, but day lilies are extremely toxic to cats and, to a lesser degree, dogs. Day lily is easily distinguished from the other common lily in Jackson Park, Michigan lilies, by the lack of spots on flowers and leaves that are basal and sword-like rather than in whorls around the stem and a horizontal orientation rather than pointing down. According to Flora of North America, day lilies were imported from Asia to Europe in the seventeenth century and to North America in the nineteenth century.

Hemerocallis

Hemerocallis fulva

day lily [Blooms: Jun-Jul]

Cow parsnip flowers are present in 6-8" wide, flat umbels (like Queen Anne's lace) that arise from the central stem or from leaf axils. Beneath each flower cluster are four or more needle-like, fuzzy green bracts; the bracts fall off after the fruit begins to form. Individual flowers are 1/4" across with five white petals that are notched at their tips; in flowers on the edge of an umbel, one petal is visibly larger than the other four. A somewhat lumpy, cream-colored, hairy ovary occupies the center of the flower from which arise two short styles; five stamens with pale yellow anthers arc laterally from under the ovary. Each fruit is heart-shaped, flattened, and contains two seeds.

Heracleum

Heracleum sphondylium

cow parsnip [Blooms: May/Jun-?]

Dame's rocket flowers occur in clusters (racemes) of up to 30. Each flower is 3/4-1" across and long, with a long, narrow, tubular, pinkish-green calyx composed of four long narrow sepals. The calyx opens through a narrow throat into four rounded, pinkish-purple (sometimes white) petals; the six pale yellow stamens and the multiple styles poke to various degrees out of the throat. Stems, leaves, pedicles, and the flower calyxes are all downy or hairy. The fruits are long (up to 4"), narrow, ascending, downy cylinders (siliques, typical of mustards) filled with flattened, oblong seeds. The flowers are very phlox-like, but phlox flowers have five petals, and dame's rocket only has four; phlox leaves are opposite on the stem (not alternate) and are narrower.

Hesperis

Hesperis matronalis

dame's rocket [Blooms: Apr-May]

Heuchera richardsonii

Heuchera

Heuchera richardsonii

common alumroot [Blooms: May – Jun]

Halberd-leaved rose-mallow is a striking wild hibiscus, usually found near water, whose stems can get 6' tall. Flowers arise from leaf axils, are trumpet-shaped, up to 5" across, with five rounded, partially overlapping white to pink petals; a central columnar reproductive structure covered in creamy-white stamens (with reddish-tan anthers) in whorls, and a terminal divided style with five recurved tips, each bearing a stigma shaped like the head of a pin. Behind the corolla is a green calyx with five lobes, and ~12 rod-like, curved, green bractlets below the calyx that taper to sharp points. The throat of the flower is a deep reddish-purple or rose pink. Seed pods form within the persistant sepals; the seed pod is divided into five sections filled with fuzzy brown seeds. The three-lobed (halberd-shaped) or five-lobed (maple leaf shaped) leaves distinguish this species from other rose-mallows. (Only swamp rose-mallow, Hibiscus moscheutos, also occurs in Jackson Park.)

Hibiscus

Hibiscus laevis

halberd-leaved rose-mallow [Blooms: Jul-Aug]

Swamp rose-mallow is a wild hibiscus that prefers wet habitats; the stem can get up to 7' tall. Flowers arise from leaf axils and are trumpet-shaped, 4-6" across with five pink or white petals (sometimes with a reddish-purple throat); and, in the center of the flower, a stout cream colored column that bears both whorls of white stamens with yellow anthers and a white style divided into five upcurving parts, each with a pin-head shaped stigma. Behind the corolla are five light green sepals and 12 awl-like 1" long bracts that curve forwards. This is the more variable of the two local rose mallows; it has white or pink flowers which may or may not have a reddish-purple throat (all are now considered the same species).

Hibiscus

Hibiscus moscheutos

swamp rose-mallow [Blooms: Jul-Aug]

Flower-of-an-hour flowers are borne singly on hairy flower stalks that arise from the leaf axils; the flowers are 2" across, with five partially-overlapping petals that are white or pale yellow with deep purple bases. Sepals are pale green, translucent, and membranous with deep purple, hairy veins. The numerous stamens are borne on a "staminal column" that surrounds the base of the style; the filaments are maroon and the anthers are golden yellow. The single style is white where it rises above the staminal column and is divided at the tip into five knobby stigmas.

Hibiscus

Hibiscus trionum

flower-of-an-hour [Blooms: Jul-Sep]

American hops male and female flowers occur on separate plants. Actual female (pistillate) flowers occur in tight clusters ("aments") 3/4" long of 10-50 flower pairs on a stalk that arises from a leaf axil, each pair subtended by a bract; each flower has two long, thin styles. Male flowers have five pale green spreading sepals and five short, banana-shaped stamens. The fruit is a cone-like structure of overlapping bracts (originally present at the base of the female flowers) that surround the seeds; it is (obviously) found only on the female plants.

Humulus

Humulus lupulus

American hops [Blooms: Jul-Sep]

Wild hydrangea canes produce a flat terminal panicle 3-6" across with 100-500 flowers of two kinds — small, fertile flowers filling most of the area and a few, sterile pseudo-flowers around the margin that are 3-4 times larger than the flowers in the center and seem to function only as an advertisement for pollinators. The central, fertile flowers are about 1/4" across with a green calyx made of five separate sepals; five greenish-white or cream petals about 1/8" long; 8-10 stamens with long filaments and oblong, white anthers; and a pistil bearing two styles with knob- or club-like stigmas. The sterile, outer pseudo-flowers have 3-4 fused petal-like, white bracts (or sepals; sources differ) with a central structures that visually is reminiscent of stamens or styles; the pseudo-flowers persist long after the inner flowers have been fertilized and have produced a two compartment seed pod that is ribbed and bears a pair of tiny horns (the styles) on its upper end. Wild hydrangea is relatively rare in northern Illinois; in Jackson Park it prefers wooded area by walking paths.

Hydrangea

Hydrangea arborescens

wild hydrangea [Blooms: Jun-Aug]

Panicled hydrangea (Hydrangea paniculata) is an exotic perennial native to China and Japan that may grow as either a shrub or a tree. Neither Natureserve Explorer nor the USDA Plants database acknowledge the presence of panicled hydrangea in Illinois, but the Morton Arboretum and the University of Illinois Extension both explicitly do. Panicled hydrangea is widely sold in nurseries; commercial cultivars reach 10-15 feet high and wide. It definitely occurs in Jackson Park, near our native species — wild hydrangea (Hydrangea arborescens) — but I have not seen it in direct competition with wild hydrangea. The inflorescence is a conical panicle typically covered with two types of flowers — large, nominally-sterile flowers and smaller, bisexual flowers — scattered across the surface of the panicle. The "sterile" flowers are white or greenish white with typically 4-5 (3 in Jackson Park) elliptical to round lobes (actually sepals) 1/2-1" long and 1/3-2/3" across (8-15 mm). In Jackson Park, at least half the nominally sterile flowers bear a small, budlike structure in their center that exhibits three lobes (petals?), have 3-6 distinct stamens with small anthers, and a two-lobed central structure that is probably a reduced pistil. It is not clear whether either the pistils or stamens are functional. The bisexual flowers usually have five tiny (less than 1 mm long and wide) sepals, five petals 3-4 mm long and 0.1-0.3 mm wide (which often fall off the flower), 2-5 mm long stamens, and an ovary with 2-4 spreading styles (two in Jackson Park specimens) that are 2-3.5 mm long and are fused at their bases. After fertilization, the petals and stamens wither and fall off; the remainder of the flower forms an oblong, 3-5 mm long, seed capsule. The easiest ways to tell panicled hydrangea (H. paniculata) from wild hydrangea (H. arborescens) is: (1) the inflorescence is conical or pyramid-shaped in panicled hydrangea but a flat disc or shallow dome in wild hydrangea, and (2) the showy, "sterile" flowers in panicled hydrangea are scattered evenly across the surface of the inflorescence in panicled hydrangea, but are restricted to the margins of the inflorescence of wild hydrangea (rather like the inflorescence of the much more common but unrelated American cranberry, Viburnum opulus var. americanum). Wild hydrangea is much more common than panicled hydrangea in Jackson Park.

Hydrangea

Hydrangea paniculata

panicled hydrangea [Blooms: Jul]

Virginia waterleaf stems are variable in color (green, reddish-green, or reddish-brown) and up to 2' tall. Each upper stem has at their tips one or two clusters (cymes) of 8-20 flowers that is 1-2" in diameter on a 4" stalk (peduncle); the central flower opens first. Individual flowers are 1/4-1/2" long, roughly bell-shaped, white, pink, or light violet in color. Flowers have a green, hairy calyx with five long, narrow teeth fringed with widely-spaced, stout hairs; a tubular corolla with five equal lobes at the open end; five stamens covered with long hairs along their lower half, with anthers initially yellow that later turn dark brown; and a single lavender style with a white, bifurcated tip. Both the stamens and the style are 30-50% longer than the corolla lobes and extend well beyond their edges.

Hydrophyllum

Hydrophyllum virginianum

Virginia waterleaf [Blooms: May]

Giant St. John's wort stems and branches terminate in clusters (cymes) of 1-5 flowers 2-2.5" across; the central bud opens first. Giant St. John's wort has the largest flower of all the St. John's worts found in Illinois. Each flower has five green sepals 1/3 the length of the petals; five bright yellow, often twisted, petals; more than 100 yellow stamens with yellow anthers; and a yellow-green pistil with five distinct styles fused at their bases, each with red stigmas at their tip. Five carpels are present in the flask-shaped ovary. The fruit is a five-chambered, bullet-shaped structure up to 1.25" long and 1/2" wide, initially green, turning brownish-black with maturity; the capsule is topped with the remnants of the (five) styles and contains numerous lozenge-shaped, 1 mm long, black seeds. (When fully mature and with appropriate magnification, the seeds look like ears of corn.) Note in particular the very large (2") flowers and the five styles on the pistil of giant St. John's wort — most other Hypericum spp. have either one or three styles. Kalm's St. John's wort also has five styles, but that is a much smaller and woody plant with narrower leaves and much smaller flowers.

Hypericum

Hypericum ascyron

giant St. John's wort [Blooms: Jun-Aug]

Kalm's St. John's wort is a 1-3 ' tall shrub, largely restricted to the Great Lakes basin of the U.S. and Canada; it is formally listed as "critically endangered" in Illinois (but is quite common in Jackson Park). The flowers occur in clusters (corymbs) of 3-7. Individual flowers are 1-1.25" across; they have five light green, lance-shaped sepals half the length of the petals, five spreading golden-yellow petals, 150-200 stamens with yellow anthers, and a five-lobed yellow ovary with five (partially or completely fused) styles. The ovary often is markedly five-lobed. The fruit is a teardrop-shaped capsule resting on the five widely-spread sepals containing five (occasionally four) carpels; the capsules are initially green, then turn bright red, then finally brown as the numerous black, oblong seeds mature. Woody lower branches and the strongly five-lobed pistil and fruit are distinguishing characters that separate this species from other Jackson Park St. John's worts.

Hypericum

Hypericum kalmianum

Kalm's St. John's wort [Blooms: Jun-Aug]

Common St. John's wort flowers are ~3/4" across, with five green sepals, five oblong yellow petals, three widely-spreading styles (and three carpels) with scarlet stigmas on top of a globular yellow ovary, and numerous (45-85) stamens with yellow anthers. The filaments of the stamens fuse into three groups near their bases. Unique among the St. John's worts in Illinois, common St. John's wort has petals with tiny black dots (glands full of essential oils) that are restricted to the petal margins. (Hypericum punctatum, spotted St. John's Wort, also has black dots on the petals but, in that species, they extend to the interior of the petals.) These black glands may also occur sparsely on the anthers. The fruit is a three-chambered, bullet-shaped structure 1/4" long, initially green, turning reddish-brown with maturity; the capsule is topped with the remnants of the (3) styles and contains numerous seeds. Common St. John's wort contains chemicals that may interact adversely with a number of common pharmaceuticals despite its widespread use in traditional medicine and may be toxic to livestock in large doses.

Hypericum

Hypericum perforatum

common St. John's wort [Blooms: Jun-Aug]

Shrubby St. John's wort is, as the name says, "shrubby;" the "prolificum" part refers to the exceptionally numerous stamens. The upper stems and axils of the two upper pairs of leaves produce clusters of 3-7 flowers. Flowers are ~1" across, with five green sepals much shorter than the petals, five yellow petals, 150-500 stamens, and a pistil with three styles united at the base and appressed along their lengths. The fruit is a capsule <1/2" long, cone shaped and tapering to the tip, with the tips of the three styles persistant, not lobed but bluntly triangular with three compartments internally (corresponding to the three carpels of the ovary). Hypericum prolificum and Hypericum kalmianum both have woody lower branches (the only Hypericum sp. that do) and are very similar vegetatively, but H. kalmianum produces a seed capsule with the remnants of five styles and has five internal compartments while H. prolificum produces seed capsules bearing the remnants of three styles and has three internal compartments.

Hypericum

Hypericum prolificum

shrubby St. John's wort [Blooms: Jun-Aug]

Round-fruited St. John's wort flowers are 1/2-3/4" across, with five (sometimes four) green sepals shorter than the petals, five rounded, bright-yellow petals with curled margins and tips, 45-85 yellow stamens with orange anthers, and a slender, flask-shaped pistil with three styles fused at their bases bearing tiny stigmas. The fruit is globular with a long, tapering neck, not a lobed bullet-shape as in other Hypericum. Descriptions of this species say it has three styles, but the populations in Jackson Park typically have flowers with what is apparently single style but close inspection (especially of older flowers) show actually has three styles, closely appressed. The styles separate at their tips late in blooming or early in the development of most fruits.

Hypericum

Hypericum sphaerocarpum

round-fruited St. John's wort [Blooms: Jun-Jul]

Orange jewelweed flowers are about 1" long and 1/2-3/4" wide, conical, bright, shiny orange with reddish or brown streaks or dots and with a posterior sac and nectar spur that are actually a modified sepal; the flowers hang from drooping pedicels like floral mobiles with two more-conventional-looking sepals as attachments. The morphological center of the flower is the point where the pedicel joins the two obvious sepals at the top of the flower. A single petal forms the upper lip of the flower; two petals form the lateral sides; and two partially fused petals form the two-lobed lower lip. A cluster of stamens with white anthers hangs from the upper lip near the aperture; there is a single pistil. The shade of orange and the extent of the darker dots and streaks are highly variable (from absent to covering the flower). The fruit is a pea-like seed pod that splits lengthwise to fling the seeds away from the plant.

Impatiens

Impatiens capensis

orange jewelweed [Blooms: Jul-Nov]

Ivy-leaved morning glory is a sprawling, green to reddish vine up to 6' long covered with long, white hairs. Flowers arise from leaf axils on very short (1/4") stalks; they are funnel-shaped, ~2" across, blue-violet with a white throat, with five stamens with white anthers and a single style with a three-lobed stigma. The calyx is about 1/2" long, divided into five long, narrow teeth. Individual flowers only last a few hours. The seed capsule has three compartments and is hairy. Sepals are relatively very long and narrow, unlike common morning glory, where the sepals are short and triangular. Ivy-leaved morning glory is also native to Central America and its history of introductions is probably similar to common morning glory, Ipomoea purpurea.

Ipomoea

Ipomoea hederacea

ivy-leaved morning-glory [Blooms: Aug-Sep]

Small white morning glory is a vine 3-8' long, covered in scattered white hairs. The flowers are much smaller (1" long and 3/4" across) than most other Jackson Park morning glories, pentagonal rather than circular in outline, white, and shallowly lobed. The flowers consist of five lance-like sepals about 4 mm long, the funnel-like corolla, five stamens with a white filament and pinkish-purple anthers, and a single style with a knobby or bifurcated stigma. Fertilized flowers produce a spherical, hairy seed capsule about 1/2" in diameter nestled in the five sepals. Unlike the other two morning glories in Jackson Park, small white morning glory is native, but uncommon in northern Illinois.

Ipomoea

Ipomoea lacunosa

small white morning-glory [Blooms: Aug-Sep]

Wild sweet potato is a twining vine that can reach 20-30' long, completely covering the adjacent vegetation. The flowers are funnel-shaped with five shallow lobes, 2.5-3" across, white with a reddish-purple or rosy throat. There are five stamens of different lengths with filaments up to an inch long and whitish-pink anthers; there is a single whitish style with a two-lobed stigma. The flowers tend to bloom early in the day, later if cloudy. Individual flowers are short lived but this plant is a prodigious producer of blooms; it is the largest morning glory in Jackson Park. The "sweet potato" is a modified root up to 20" long and weighing 30 pounds; it is edible, but only barely.

Ipomoea

Ipomoea pandurata

wild sweet-potato [Blooms: Jun-Aug]

Common morning glory is a vine up to 10' long with alternate, heart-shaped (never lobed), smooth-margined, almost as wide as long. The stem is green or reddish-purple, covered with long hairs; it twines around adjacent vegetation and objects. Cymes of 1-5 flowers arise from some leaf axils; they sit at the tip of about 4" long pedicels. The flowers are 2-3.5" wide, funnel-shaped, usually deep purple or pink, less commonly blue or white, a single style with a three-lobed stigma, and five stamens. Sepals are relatively short, hairy, and triangular unlike ivy-leaved morning glory (I. hederacea), where the sepals are long and narrow. Other morning glories (Ipomoea sp.) usually have lobed leaves; the superficially-similar bindweeds usually have arrowhead-shaped leaves, not heart-shaped. Common morning glory has sepals that are short and triangular, unlike ivy-leaved morning glory where the sepals are relatively very long and narrow. Common morning glory is native to Mexico; it was introduced to England by 1621, then introduced from England to North America around 1700 as an ornamental (Fang et al., 2013), where it rapidly escaped cultivation.

Ipomoea

Ipomoea purpurea

common morning-glory [Blooms: Aug-Sep]

Yellow iris might be mistaken for simply a yellow variant of blue flag iris, but the two species are distinct. Yellow iris has basal leaves longer (3-4') than the flower stalk; both prefer wetlands and shallow water. The leaf venation is parallel, typical for a monocot. As you would expect, the flowers are yellow with golden patches. Each flower stalk bears branches that terminate in clusters of 2-3 flowers. Each flower is 3-4" across and consists of: (1) three yellow sepals (the "falls") drooping towards their ends with a conspicuous golden spot (the "signal") whose edge is outlined by a series of brown to maroon spots or lines; (2) directly above the sepals are three yellow petal-like style branches (the "style arms") with upturned tips (the "style crests") (the stigma, where pollen is captured, is located at the fold between the style arms and crests); and, (3) between the sepals are three very short yellow petals (the "standards") that barely rise up above the plane of the sepals and style branches. The stamens are located under the style arms. The seed capsules are three-lobed, elongate (3") ovals that contain seeds that float on the water when released. Yellow iris is an introduced plant from Europe, now naturalized.

Iris

Iris pseudacorus

yellow iris [Blooms: May-Jun]

Iris virginica is the typical "blue flag" iris; it is an impressive plant 2-3' tall that prefers wetlands and shallow water. Each flower is 3-4" across consisting of: (1) three sepals (the "falls") that whose ends droop, each with a conspicuous bright-yellow spot (the "signal") and blue lines lead from the edges of the sepal into the signal; (2) directly above the sepals are three blue-violet petal-like style branches (the "style arms") with upturned tips (the "style crests") (the stigma, where pollen is captured, is located at the fold between the style arms and crests); and, (3) between the sepals are three petals with dark purple veins (the "standards") that rise up above the plane of the sepals and style branches. A green, ovoid ovary occurs at the base of the sepals and petals. The stamens are located under the style arms. The seed capsules are three-lobed, elongate ovals 2-3" long that contain seeds that float on the water when released. Blue flag iris (Iris virginica) is native to Illinois and Missouri, but it is sometimes confused with the very similar Iris versicolor; however, the Illinois Department of Natural History does not recognize Iris versicolor as occurring in Illinois. (It is present in Wisconsin and Minnesota.)

Iris

Iris virginica

blue flag iris [Blooms: May-Jun]

Black walnut has separate male and female flowers on the same tree (often the same branch). The male florets occur on 3-6" long, dangling, green, cylindrical catkins that arise from the leaf axils of one-year-old branchlets; the florets are 1/8" across and are comprised of a short, tubular calyx with 2-6 lobes and 15-40 stamens with greenish-yellow or purplish anthers. The female florets occur in groups of 2-5 on short spikes that arise from the tips of the current year's new branchlets; these florets are also about 1/8" across but are comprised of a short, tubular calyx with four lobes, a stout, green ovary covered with sticky hairs, and a pair of stout, bushy styles with red-tinged stigmas. The female florets are wind pollinated; the trees are self-fertile if cross-pollination does not occur. Fertilized female florets develop into globoid nuts about 2.5" long and 2" across that initially retain the styles; the nuts are solitary or in pairs. The thick husk turns from green to yellowish-brown to black as the fruit matures. The nuts cannot germinate unless they are exposed to 90-120 days of cold winter temperatures.

Juglans

Juglans nigra

black walnut [Blooms: May?-Jun]

Dudley's rush culms (stems) vary from 8-30" tall, unbranched except for the inflorescence, light green, hairless, and round in section. At the base of the culm are one or two 12" long, 1 mm wide, flat basal leaves. The sheath of the leaves clasps the bottom inch or two of the culm; they may be light green, light brown, or tan; at the top of the sheaths are tiny, thick, cartilaginous ear-like lobes less than 0.5 mm wide. At the culm's apex is a branched inflorescence with 6-80 flowers. At the base of the inflorescence are 1-3 narrow bracts; at least one of the bracts extends beyond the inflorescence. Individual flowers are about 1/4" across, solitary at the end of short branches, each with six 4-5 mm long tepals in two layers, six stamens, and a pistil with a singe style; they are wind pollinated. The tepals spread somewhat as the fruit is developing.

Juncus

Juncus dudleyi

Dudley's rush [Blooms: May-Jun]

Soft rush can be 2-4' tall, often growing in clumps of culms. Culms terminate in an inflorescence 3/4-4" across and an underlying bract 4-12" long that looks more like an extension of the culm than a leaf so the inflorescence looks like it is growing out of the side of the culm. Individual flowers are 2-3.5 mm long with three lance-shaped sepals, three lance-shaped petals, three stamens, and single style emerging from a central ovary; the flowers are wind pollinated. Color of these elements varies from green to brown depending on stage in the life cycle; sepals, petals, and the ovary/capsule are all about the same length at maturity.

Juncus

Juncus effusus

soft rush [Blooms: May-Jun]

Path rush (aka, slender path rush, poverty rush) is a native perennial 4-12" tall. It occurs singly or in dense tufts; the culms are light to medium green, slender, and unbranched. The leaves are considered basal by some sources, alternate by others, slender (about 1 mm across and up to 10" long), medium green, hairless, and flat with margins that tend to roll upwards. Fertile stems bear a branched inflorescence at their tips that is 1/2-3" across, bearing an umbel-like cluster of up to ten solitary flowers (never larger groups); at the base of the inflorescence is three slender, leafy bracts up to 4" long (the larger are longer than the inflorescence) that form a "V". Individual flowers have six lance-shaped, light green tepals, 3-5 mm long; six stamens; and an ovary (later a seed capsule) with a three-part, feathery style. Fertilized flowers produce an ovoid seed capsule nestled in the crown-like tepals, often with a tiny point at its tip; it is never longer than the tepals. The seed capsule later splits in three segments, releasing the tiny (0.5 mm) seeds.

Juncus

Juncus tenuis

path rush [Blooms: ?-Jun]

Torrey's rush is 2-3' tall, with robust stems that are deep green, hairless, and circular in cross section; each stem bears 2-5 alternate leaves and 1-3 basal leaves. The central stem branches rapidly at its tip; each branch ends in a spherical flowerhead about 1/2-3/4" across. The lowest flowerhead in the array sits above a very long, thin bract (main image). There may be up to 23 flowerheads in the array. Individual flowerheads are composed of 25-100 florets that each have six stamens, a narrow ellipsoid ovary with a 3-part stigma (center of insert), and six tepals (sepals and petals) in two layers; all tepals are green, bract-like, lance-shaped, and 3-6 mm long. The flowerheads are more bristly than flower-like in appearance. The flowers are wind-pollinated. After fertilization, flowerheads turn brown and look very spikey.

Juncus

Juncus torreyi

Torrey's rush [Blooms: Jul-Aug]

American water-willow produces long (up to 6") peduncles from some of the upper leaf axils that have clusters of flowers on their tips. Individual flowers are 3/4" across with a short, tubular, 1/4" long, green calyx with five teeth and a tubular corolla with four lobes — an upper lobe with a shallow V-notch, two widely spreading lateral lobes, and one lower lobe at right angles to the other three. Both the lateral and lower lobes are folded downward along their midlines, producing a U-shaped cross-section. All of the lobes are white or pale purple with a darker splotch on the end of the upper lobe and dark purple spots along the midline of the lower lobe and at the base of the lateral lobes. There are two stamens, each with a dark brown pair of anthers posed in front of the upper corolla lobe and a single, narrow, white style running along the midline off the upper lobe and protruding beyond its upper boundary.

Justicia

Justicia americana

American water-willow [Blooms: Jun-Aug]

Kochia's greenish-yellow flowers are 4-5 mm across. Perfect flowers have five green, bluntly-triangular sepals that develop wings along their outer face, no petals, five stamens each with two large yellow or pink anthers, and a divided style; pistillate flowers lack the stamens. The flowers are wind-pollinated. The fruit is a flattened, five-lobed, winged capsule nestled in the sepals that contains a solitary seed. ITIS says that the accepted name for this plant is Kochia scoparia; World Flora Online claims the proper binomial is Bassia scoparia.

Kochia

Kochia scoparia

kochia [Blooms: Jul-Aug]

Two-flowered cynthia is a yellowish-orange dandelion-like composite flower consisting of only ray florets. Each of the 25-60 ray florets is elongate with a truncated tip with five tiny teeth; the stamens are orange and the styles have bifurcated tips. The basal leaves are hairless, up to 7" long and 2" across, with a broad, rounded tip; the base of the leaf narrows into winged petioles that clasp the stem. The margins of the leaves are nearly toothless. The 1-2' tall stems arise from the center of the basal rosette. One to six 1" wide flowers sit on stalks that emerge from an upper stem leaf axil where one or two lance-shaped leaves clasp the stem; unusually, only two flowers are open at any one time. The yellow-orange color is distinctive; most other dandelion-like flowers are yellow.

Krigia

Krigia biflora

two-flowered cynthia [Blooms: Jun-?]

Canada lettuce gets up to 8' tall (and is quite impressive when it does), but is usually considerably shorter. On larger plants, the inflorescence is an apical pyramid 2' tall covered with dandelion-like flowerheads; on smaller plants the flowerheads may be more scattered. Flowerheads are yellow or "dirty orange," a bit over 1/4" wide with a 1/2" long calyx and 15-22 ray florets with toothed tips, each with five stamens and a bifurcated style; there are no disc florets. Seeds are oval, flattened, and attached to a tuft of threads (like a dandelion). Small Canada lettuce plants are superficially similar to prickly lettuce (Latuca serriola), but the latter has large spines on the underside of the main veins of the leaves and seeds that are attached to the tuft of hairs by a beak twice as long as the seed.

Lactuca

Lactuca canadensis

Canada lettuce [Blooms: Jul-Sep]

Prickly lettuce flowerheads dandelion-like, a distinctive pale lemon-yellow color, and 1/4-1/2" across; there are about 20 ray florets with squared, serrated ends (with five teeth), five stamens with yellow anthers, and a bifurcated style whose base is surrounded by the anthers. The seeds are attached to the tuft of hairs by a beak up to twice as long as the seed. Prickly lettuce is superficially similar to Canada lettuce (Latuca canadensis), but the latter has no spines on the leaves and seeds that are attached to a tuft of hairs by a beak no longer than the seed. Prickly lettuce is the closest wild relative to domestic lettuce (L. sativa).

Lactuca

Lactuca serriola

prickly lettuce [Blooms: Jul-Sep]

Henbit's vertically-oriented flowers occur in clusters of 4-10 at the top of stems. They are tubular, 1/2-3/4" long, initially narrow at the short, five-lobed green calyx, but broadening into a hood-like upper lip that is densely covered with short hairs and a drooping lower lip that broadens into two lobes. The stamens are attached to the base of the lower lip but have long filaments so that the purplish anthers are positioned just under the upper lip; the style is white, about 3/4" long, with a two-lobed stigma. The outer surfaces of the flower are purplish-pink to pink; the inner surfaces are white with purplish dots. The fruit is a cluster of four nutlets, each containing a single seed.

Lamium

Lamium amplexicaule

henbit [Blooms: Apr-May]

Purple dead-nettle's whorls of flowers occur in the leaf axils and at the tip of the stem. Flowers are about 1/2" long with a short, five-lobed green calyx and a tubular, purplish pink to white corolla with an upper and lower lip; the lower lip is divided into two lobes, often white with purple spots. There are four short stamens with brown anthers positioned beneath the upper lip and a single style with a two-lobed stigma. The closely-related henbit (Lamium amplexicaule) has much longer tubular flowers and leaves that are sessile or clasp the stem rather than being borne on petioles. The "dead-nettle" name comes from a resemblance of the leaves to some nettles, but the lack of stinging hairs (thus, a dead nettle).

Lamium

Lamium purpureum

purple dead-nettle [Blooms: Apr-?]

Wood nettle plants may be either monoecious (separate male and female flowers on the same plants) or unisexual (only male or only female flowers). Male flowers are produced from branching cymes 4" long that arise from the leaf axils; female flower are produced from branching cymes, also 4" long, localized near the apex of the stem. Male flowers are small (1/8" across), consisting of five narrow, greenish-white sepals and five stamens; there are no petals but there is a vestigial pistil. Female flowers are about the same size (1/8" across) with four green sepals (two larger, two smaller) that look like tiny leaves with undulating edges and an ovary with a long, white, vertically-oriented J-shaped style that tapers to a point. The female flowers are wind-pollinated. The fruit is circular in outline but very flattened, green turning black with maturation, on a short winged stalk; the remains of the style are attached at the free end of the fruit.

Laportea

Laportea canadensis

wood nettle [Blooms: Aug-Sep]

Duckweed is a tiny, floating flowering plant (one of the smallest in the group) that is present on the lagoons and Columbia Basin from May through October. The flower is highly reduced — about 1 mm across consisting of a cup-shaped scale, a pair of tiny stamens, and a single pistil; I have never observed it. (The flowers are rarely produced — most reproduction is vegetative.) The combination leaf and stem is oval, 2-5 mm long and 1.5-3.5 mm across with a single rootlet up to 2 cm long dangling from the underside. Unless you have a good magnifying glass or microscope, further detail will not be useful.

Lemna

Lemna minor

duckweed [Blooms: ?]

Motherwort is a naturalized exotic from Eurasia with stems up to 5' tall (more commonly 3-4'); branches occur near apex, if they are present at all. The flowers are sessile; they occur in whorls just above a pair of opposite leaves in the upper half of the plant, almost completely covering the stem. Individual flowers are about 3/8" long, two-lipped and VERY hairy on the outer surfaces with profuse long, white hairs; the upper lip is reflected backwards and unlobed, while the lower lip is divided into three lobes. The lips are white or light pink with purple spots on the lower lip and purple mottling on the upper lip. Four stamens with purple anthers protrude about half way up the upper lip; there s a single style with a two-lobed stigma that is located between the two longest stamens. The stubby, tubular calyx has five very sharp lobes/spines lending a touch of danger to the flowers; after fertilization, the calyx holds four nutlets, each containing a single seed. Motherwort was introduced from Europe (where it was previously introduced from Asia) primarily as a medicinal herb; it is now considered invasive. Motherwort could possibly be confused with field mint (Mentha arvensis) but field mint lacks the distinctive three- or five-lobed angular-cleft leaves of motherwort and has boldly-protruding stamens that are lacking in motherwort.

Leonurus

Leonurus cardiaca

motherwort [Blooms: Jun-Aug]

Field peppergrass tems produce racemes of flowers near their apex; flowers near the top of the raceme are the youngest with older flowers (and later seed pods) further down the inflorescence. The flowers have a calyx of green or purple-green, lance-like sepals, four white, spoon-shaped petals, six stamens, and a single style. The fruits are flattened pods oval in outline with the remnants of the style protruding from a notch in the end (rather like field pennycress, Thlaspi arvense); each seedpod contains two seeds. This is an easy plant to overlook if only because it look like the weed that it is.

Lepidium

Lepidium campestre

field peppergrass [Blooms: May-?]

Peppergrass (aka, Virginia pepperweed) is a weedy, 1.5' tall, rather bushy plant. The flower spikes (racemes) are 2-4" long with tiny (<1/8") white apical flowers forming a larger inflorescence. The flowers have four oblong green or tan sepals with a white edge, half the length of the petals, alternating with four white, triangular petals. There are two stamens with yellow anthers and a stubby (0.2 mm tall) style on a green ovary. Below the flowers, the flower spike is covered with 1/8" wide seedpods on (relatively) long stalks, reminiscent of a bottlebrush; the seedpods are oval with an apical notch (much like half-sized versions of field pennycress (Thlaspi arvense) seedpods) containing two seeds. This species is native to the U.S. The stubby cylindrical inflorescences are and the triangular petals alternating with shorter sepals are diagnostic and distinguish pepper grass from field peppergrass (Lepidium campestre).

Lepidium

Lepidium virginicum

peppergrass [Blooms: Oct-Nov]

Round-headed bush-clover present stout, tall (2-5') green columns in the middle of open habitats. The stem is unbranched below the midpoint (except at the inflorescences), round in section, grooved, and densely covered in white hairs. At the apex of the main stem and on some of the side stems are slightly elongated balls of flowers 3-5" long and half as wide with numerous clover-like white flowers nearly hidden among leafy bracts; brown flowerheads and stalks may persist through winter. Each clover-like flower is about 1/4" wide and 1/2" long with five petals, one large vertical upper petal ("standard") and two perpendicular side petals ("wings") are visible; the other two petals (forming the keel) are hidden from view by the wings. There are ten stamens, all but one with their filaments fused together, and a single style with a small stigma. The petals are white with a patch of reddish-purple near the junction of the three visible petals. The fruit is a fuzzy pod less than 1/4" long containing a single seed. Round-headed bush-clover is a perennial with a tap root that may go down two meters into the soil.

Lespedeza

Lespedeza capitata

round-headed bush-clover [Blooms: Aug-Sep]

Violet bush-clover produces racemes or sparsely branched panicles of 3-8 flowers from the tips of stems or axils of middle or upper leaves; the inflorescences are borne on long peduncles that extend above/beyond the leaves. Individual flowers are 6-10 mm long and pea-like; they include a light green calyx with five teeth that is half the length of the flower; five whitish purple to purple petals (one upright banner with a basal patch of rosy purple; two lower, outer wings shorter than the keel; and two lower, inner petals that make up the keel); 10 stamens; and a pistil with a single style. Both the stamens and style are usually hidden within the keel. Fertilized flowers produce small green, single-seeded seedpods that lack sticky hairs (unlike the much-larger tick-trefoils); at maturity, the seedpods are 4-7 mm long and dark brown.

Lespedeza

Lespedeza frutescens

violet bush-clover [Blooms: Aug-Sep]

Ox-eye daisy is an aggressive plant that was introduced to the U.S. in the 19th century and is now thoroughly naturalized. Flowerheads occur singly at the apex of the stem on a long flower stalk. The flowerheads are about 1.5-2" across with 15-35 brilliant white, oblong ray florets and 120-200 yellow disc florets in a central, flattened disc about 3/4" across. The ray florets are fertile (they bear pistils with a split stigma) while the disc florets have both pistils and stamens. The disc florets are tubular with five tiny lobes at the apex, five stamens, and a single style with a bifurcated tip. The underside of the flower has numerous bracts in 2-4 layers; the bracts are green with purple to brown edges that outline each bract.

Leucanthemum

Leucanthemum vulgare

ox-eye daisy [Blooms: May-Jul]

Despite its common name, summer snowflake starts blooming in the spring (late April), not the summer. It is an introduced species, native to Europe and west Asia, similar in appearance to snowdrops (Galanthus nivalis) but larger. The leaves are exclusively basal, up to 12" long and an inch wide, flattened, arching, dark green, sheathing the base of the stems which may be the same length but are usually shorter than the leaves. The flowers dangle from the tips of hollow flower scapes in groups of 2-5, subtended by a single green, sword-shaped, spathe-like bract. Each flower has three sepals and three petals (white, pointed, with a yellowish-green spot near their tips), six stamens with orange anthers, and a single style with a green tip and a tiny stigma. Summer snowflake is toxic if ingested (like many lilies).

Leucojum

Leucojum aestivum

summer snowflake [Blooms: Apr-May]

Lyme grass flower spikes are 5-14" long, initially blue-green or silvery but turning beige when mature. There are typically one pair of spikelets per node on the spike. The spikelets are 1/2-1" long, containing 2-5 (typically 3) florets; each floret contains two bottlebrush-like styles and 1-3 stamens, each typically with a single yellow anther. Like all grasses, Lyme grass is wind pollinated. Lyme grass is very similar to the native American dune grass (Leymus mollis) but the latter is greener and is finely hairy under the spike. Lyme grass has become established in sandy habitats around the Great Lakes and (curiously) along the coast of Greenland.

Leymus

Leymus arenarius

Lyme grass [Blooms: May-Jun]

Rough blazing star's floral spike grows directly from the stem 6-18" long, with composite flowerheads along its length. Very early buds may appear as white, miniature cabbage-like structures, with purple highlights. Flowerheads open from the apex and proceed in a wave towards the base of the inflorescence. Flowerheads are about 1" across and usually stalkless. They are composed entirely of 25-40 disc florets (no ray florets), each with a tubular pinkish-purple corolla with five sharply-pointed apical lobes; a very long divided style emerges from the center of the corolla and the five brown anthers are inserted side by side around the base of the style. The exterior of the flowerhead is covered with 4-5 overlapping series of green or purple-tinged broadly rounded bracts whose edges are rolled in and rough with series of distinct, tiny teeth. Rocky Mountain blazing star's bracts look very similar to rough blazing star's, but the flowerheads of rough blazing star are essentially sessile (flower stalk no more than 1/4" long) while the flowerheads of Rocky Mountain blazing star have significant stalks, most commonly 1/2-1" long (as long as the flowerhead). The Jackson Park blazing stars bloom in the order cylindrical, prairie, rough, marsh, and Rocky Mountain; in relative abundance, rough is the most common, followed by cylindrical, prairie, marsh, and Rocky Mountain. Quick key to the Jackson Park blazing stars: bracts covering base of the flowerhead are (1) sharply pointed (-> cylindrical), (2) recurved away from flower, flaring (-> prairie), (3) tip round, closely appressed (-> marsh), (4) margins with tiny teeth, rolled under (-> rough if flower stalk is very short, Rocky Mountain if flower stalk about same length as flowerhead).

Liatris

Liatris aspera

rough blazing-star [Blooms: Aug-Sept]

Cylindrical blazing star is a more open plant than the other Jackson Park blazing stars, with the flowerheads relatively widely spaced along the 2-4" long racemes that are perched atop a 1-1.5' tall, unbranched stem. The showy flowerheads are pink or purplish-pink, about 1/2-3/4" in diameter, sessile or held on up to 3/4" stalks, with 15-25 disk flowers and no ray flowers; the base of the flowerheads is covered with 5-7 layers of scale-like, overlapping bracts with a sharp tip that together form a slim cylinder ~3/4" long and 1/3" diameter. The disk florets are tubular with five recurved triangular flaps at their apex; a pinkish white style, surrounded at its base by the five closely-packed yellowish-brown anthers and divided distally into two long filaments. Cylindrical blazing star appears to prefer dryer, well drained soils. The Jackson Park blazing stars bloom in the order cylindrical, prairie, rough, marsh, and Rocky Mountain; in relative abundance, rough is the most common, followed by cylindrical, prairie, marsh, and Rocky Mountain blazing stars. Quick key to the Jackson Park blazing stars: bracts covering base of the flowerhead are (1) sharply pointed (-> cylindrical), (2) recurved away from flower, flaring (-> prairie), (3) tip round, closely appressed (-> marsh), (4) margins with tiny teeth, rolled under (-> rough if flower stalk is very short, Rocky Mountain if flower stalk about same length as flowerhead).

Liatris

Liatris cylindracea

cylindrical blazing-star [Blooms: Jul-Aug]

Rocky Mountain blazing star (aka, northern plains blazing star) is the least common of the blazing stars in Jackson Park. Flowerheads lack ray florets but have 30-100 disc florets. Rocky Mountain blazing star flowerheads most closely resemble those of rough blazing star in that the bracts covering the base of the flowers in both have their edges rolled under with toothed edges, but the bracts in Rocky Mountain blazing star tend to flatten with age. The best way to distinguish the two species is by the length of the flowerhead's stalk —  the flowerheads of rough blazing star are essentially stalkless (stalks 1/4" long max) while those of Rocky Mountain blazing star are typically 1/2-1" long or longer, often the same size or longer than the flowerhead itself. Illinois is on the eastern edge of Rocky Mountain blazing star's range, so it's a fairly rare sight here. Quick key to the Jackson Park blazing stars: bracts covering base of the flowerhead are (1) sharply pointed (-> cylindrical), (2) recurved away from flower, flaring (-> prairie), (3) tip round, closely appressed (-> marsh), (4) margins with tiny teeth, rolled under (-> rough if flower stalk is very short, Rocky Mountain if flower stalk about same length as flowerhead).

Liatris

Liatris ligulistylis

Rocky Mountain blazing-star [Blooms: Aug-Sep]

Prairie blazing star's stem ends in a spike of composite, purple flowerheads 1/4-1/2" across; pinkish-red bracts cover the underside of the flowerheads, tapering to a fine tip that dramatically curls away from the flowerhead (like the scales on a dry pine cone). (No other blazing stars have such recurved bracts.) Each flowerhead has 5-10 disc florets that are tubular, 7-10 mm long, with five lobes at the apex forming a prominent star shape. A hairy, divided style protrudes well beyond the apex of the corolla; the base of the style is surrounded by the 3 mm long, reddish-brown anthers of the five stamens. Prairie blazing stars prefer well-watered areas. The Jackson Park blazing stars bloom in the order cylindrical, prairie, rough, marsh, and Rocky Mountain; in relative abundance, rough is the most common, followed by cylindrical, prairie, marsh, and Rocky Mountain. Quick key to the Jackson Park blazing stars: bracts covering base of the flowerhead are (1) sharply pointed (-> cylindrical), (2) recurved away from flower, flaring (-> prairie), (3) tip round, closely appressed (-> marsh), (4) margins with tiny teeth, rolled under (-> rough if flower stalk is very short, Rocky Mountain if flower stalk about same length as flowerhead).

Liatris

Liatris pycnostachya

prairie blazing-star [Blooms: Jul-Aug]

Savanna blazing-star's inflorescence is a long (up to 24"), narrow raceme of 10-40 flowerheads blooming in order from the tip of the inflorescence downwards. Each flowerhead has a 1/2-3.5" long, ascending stalk (peduncle); flowerheads are usually solitary on the peduncle. A sessile, leafy bract resembling the leaves occurs at the base of each peduncle. The central stalk of the inflorescences and the peduncle are fuzzy with short, white hairs. Each flowerhead is 1-2" across; they have 20-80 disk florets and no ray florets. The disk florets are tubular with five narrow, spreading lobes. The styles are bifurcated and extend well beyond the corolla of the disk florets, giving the flowerheads a shaggy aspect. There are five stamens hidden within the throat of the disk floret; the black anthers are visible, appressed to the body of the style. Surrounding the base of the flowerhead are scale-like bracts (phyllaries) in 4-6 overlapping series; they are slightly spreading and angled upwards but are neither appressed nor recurved. Individual phyllaries are oval or egg-shaped with short hairs protruding from their margins; they are often dark purple when the flowerhead is blooming. The fruit is a cylindrical, black seed with a tuft of white hairs about twice as long as the seed on one end. Preferred habitats are sandy savannas. Skippers and monarch butterflies seem particularly fond of savanna blazing-star. Savanna blazing-star might be confused with the much more common rough blazing star (Liatris aspera), but the latter always has appressed phyllaries with toothed, incurved edges, in contrast to savanna blazing-star's spreading, flat phyllaries and a much shorter stalk beneath the flowerhead than is present in savanna blazing-star. NatureServe Explorer (https://explorer.natureserve.org) rejects the name "Liatris scariosa" in favor of "Liatris novae-angliae" but ITIS (www.itis.gov)rejects the latter, as does the USDA Plants website(https://plants.usda.gov/). Here we will follow the latter two sources.

Liatris

Liatris scariosa

savanna blazing-star [Blooms: Aug]

Marsh blazing star flower spikes are 4-18" long extensions of the main stem, crowded with pinkish-purple flowerheads facing in all directions. Individual flowerheads are about 8 mm across; ray florets are absent and the 4-10 disc florets dominate. The corolla of a disc floret is tubular with five lance-shaped apical lobes; the divided style extends well outside the tubular corolla, surrounded at its base by five tightly packed stamens. The base of the flowerhead is covered with overlapping, flattened, elongate-oval bracts with rounded tips. Marsh blazing star is similar to prairie blazing star in appearance, but the bracts of prairie blazing star are highly recurved (like the scales on a dry pine cone). Quick key to the Jackson Park blazing stars: bracts covering base of the flowerhead are (1) sharply pointed (-> cylindrical), (2) recurved away from flower, flaring (-> prairie), (3) tip round, closely appressed (-> marsh), (4) margins with tiny teeth, rolled under (-> rough if flower stalk is very short, Rocky Mountain if flower stalk about same length as flowerhead).

Liatris

Liatris spicata

marsh blazing-star [Blooms: Aug]

Michigan lily is a moderately tall (up to 4.5'), slender, graceful plant. The flowers are 2-3" wide, dangling from 4-8" long stalks shaped like a shepherd's crook. The six tepals are yellow-orange to orange-red with purplish-brown spots scattered across their surface; the tips of the tepals are strongly recurved so the tips almost touch the base of the flower. There are six stamens with greenish-white filaments and large (1/2" long), reddish-brown anthers; a robust, yellowish-white style with a large 3-lobed, orange-red stigma. The 1.5" long seedpods are six-lobed, egg-shaped, and internally divided into three compartments. The Illinois Wildflowers website (www.illinoiswildflowers.info/) says that Michigan lily is "uncommon" but it is widespread on Wooded island and the west shore of West Lagoon in Jackson Park. Michigan lilies are easily distinguished from day lilies (Hemerocallis fulva) by the abundant spots on the tepals of the former, the tepals recurved so that they nearly touch the flower base, and the presence of stem leaves deployed in whorls along the stem.

Lilium

Lilium michiganense

Michigan lily [Blooms: Jun-Jul]

Butter-and-eggs (aka, toadflax) is an exotic, native to Europe and Asia. The stem is 1-2' tall, usually unbranched, terminating in an elongate (3-6" long) flower spike. The 1" long, yellow and orange, snapdragon-like flowers with a long nectar spur are distinctive. The vertically-oriented, tubular corolla has an upper and lower lip, each divided into two lobes that curve away from the axis of the flower. There are four fertile stamens of two distinct lengths hidden inside the corolla and a single style. The flowers are mostly pollinated by bumblebees, which are strong enough to push their way into the flower and have a long enough tongue to access the nectar.

Linaria

Linaria vulgaris

butter-and-eggs [Blooms: Jul-Oct]

Spicebush is a highly branched, woody shrub that reaches heights of 5-15'. It blooms very early in the spring — March and April in Jackson Park, before most plants have leafed out — so it is one of the few spots of color in a grey landscape. When spicebush blooms, leaves are not yet present; the small clusters of yellow flowers have the stage all to themselves. Some specimens have only a single sex of flower (pistillate or staminate); less commonly, spicebush plants may bear "perfect" flowers with both functional male (stamens) and female (pistils) organs. Individual flowers are about 1/4" across, pastel-yellow, with six yellow, petal-like tepals. Male flowers have nine stamens in three groups of three, each group associated with a two-lipped, yellow nectary; The anthers are bright yellow. Female flowers have an ovary with a single pistil and 6-18 non-functional pseudo-stamens; the stigma is large, bright white, and rough-surfaced. The flowers are said to have "an unusually sweet fragrance." The fruit is a fleshy drupe with a single stone; it turns bright red in the late summer/early fall.

Lindera

Lindera benzoin

spicebush [Blooms: Mar-Apr]

Tulip trees are the tallest native hardwood — one living specimen is 190' tall, the tallest tree east of the Mississippi. (Most tulip trees are in the 80-100' range). Illinois is on the western edge of tulip trees' range, but it is the state tree of Indiana (and Tennessee). Tulip trees have a single trunk and (usually) a pyramidal crown; the bark is gray with whitish furrows. Flowers arise on short stalks in leaf axils. Each flower is bell-shaped, erect, 2-3" across, and ~2.5" tall; there are 9 tepals — 3 pale green sepal-like tepals reflected downward and 6 fleshy petal-like tepals, yellowish-green to green in their upper half with an broad orange stripe below; the very base of the petal is pale yellow-green. In the middle of the flower is a tall (2.5") conical cluster of 60-100 pistils (the receptacle); surrounding the receptacle are 20-50 white stamens with yellow anthers. The fruit is a 1.5" long winged seed (samara) reminiscent of an ash seed; the ovate seed lies at one end of a long, thin wing with a central ridge. The leaves alone are sufficient for a confident identification; in flower or in the fall when the receptacle has produced a crown-like circlet of woody, persistant basal samaras, tulip trees are unmistakable.

Liriodendron

Liriodendron tulipifera

tulip tree [Blooms: June]

Liriope spicata is native to east and south-east Asia but was introduced to North America (specifically Illinois and Alabama) as a ground cover — it is perennial and evergreen. A single plant grows 6-18" tall and 12-24" across; it does not tolerate foot traffic. The arching leaves are dark green, grass-like, 18" long and 1/4" across, with minutely-serrated edges and parallel venation. The inflorescence is a spike-like, brownish-white rachis covered with off white or pale lavender flowers. The flowers have six elongate oval tepals, six stamens with yellow anthers, and a stubby white style about the same length as the stamens. The fruit is a berry that is initially green, turning blackish as it matures.

Liriope

Liriope spicata

creeping lilyturf [Blooms: Aug-Sep]

Hairy puccoon flowers are 3/4" across with a VERY hairy, green calyx with five sharply-triangular teeth , a yellow to yellow-orange tubular corolla with five widely-spreading rounded lobes, five stamens hidden inside the corolla beneath the throat, and a single style with a two-lobed, disc-like stigma. The flowers of hairy puccoon are heterostylous; i.e., either they have long stamens (~14 mm) and a short style (2-5 mm) or short stamens (~3 mm) with a long style (5-12 mm), but neither the anthers nor the stigma extend beyond the throat of the corolla (although they may get close). Hairy puccoon is very similar to hoary puccoon (L. canescens) but with stems that are less hairy and the hairs are "disorganized." The calyx at the base of the floral tube are very hairy in both species, but the teeth of the calyx in L. caroliniense have a distinct keel running down their midline. (I.e., subspecies L. caroliniense croceum.) Flowers of hairy puccoon are larger — up to 1" vs. 1/2" in hoary puccoon. The fruit is an egg-shaped nutlet, white when mature.

Lithospermum

Lithospermum caroliniense

hairy puccoon [Blooms: May-Jun]

Wild leeks (Allium tricoccum) (a.k.a., "ramps") is an herbaceous native perennial found in the north-east quarter of the U.S. and the eastern provinces of Canada. It is most common in moist hardwood forests but is threatened by over-harvesting. It is listed as "Vulnerable in Illinois" [https://explorer.natureserve.org/Taxon/ELEMENT_GLOBAL.2.138691/Allium_tricoccum_var_tricoccum]. In early spring, the bulb of a wild leek produces 2-3 leaves that are each 4-9" long and 1.5-3.5" across with petioles that are reddish to maroon, hairless, and wrapped in a sheath basally. The leaves wither by early summer (before flowering). Later (early to mid-summer) the bulb produces a naked flower stalk 6-18" tall; the stalk is hairless, circular in section, and pale green to maroon with a papery sheath at its base. At the apex of the stalk is a single, spherical umbel, 1-2" across, of 20-40 white flowers, with a pair of bracts at the base of the umbel when fresh. Individual flowers are about 1/4" across; the flowers contain six white to translucent tepals (6-7 mm long, three with a reddish tip); a light green to pale yellow ovary; six, 6 mm long, stamens with pale yellow anthers that extend beyond the tips of the tepals; and a single, white 3-4 mm long style that extends past the three lobes of the ovary but not beyond the anthers. The stigma tiny and spherical. Fertilized flowers produce a three-celled seed capsule, each cell containing a single globoid seed that turns glossy black at maturity. Wild leeks are denizens of hardwood forests with rich, loamy soils. The leaves and bulbs are edible, but you really shouldn't — this plant depends on only a couple of weeks of photosynthesis to produce its leaves and flowers and is highly vulnerable to overexploitation by humans. If you see one of these plants, smile and know that you have been blessed. Then walk away.

Allium

Allium tricoccum

wild leeks [Blooms: Jun?]

Cardinal flower is an unmistakable bright red (rarely white), orchid-like flower that prefers wet habitats. A mature plant is 2-3.5' tall; the stem is light green, round in section, and hairy. The stem terminates in a 1/2-1.5' long raceme of bright red flowers. At the base of the flower is a green calyx with five very long, narrow, usually-spreading lobes. The corolla is 1-1.5" long and 3/4-1" across; it is strikingly vertically-oriented. Rising above the two lateral corolla lobes and a third, three-lobed, central lip is a tubular structure that contains the fused filaments of the five stamens; the anther tubules are brush-like grayish structures at the downturned tip. The stigma runs up the center of this tube; it remain hidden for a time behind a pair of lips for a time, then the style elongates and emerges from the tip of the tube as a two-lobed stigma. The reproductive structures are precisely positioned to touch (and transfer pollen with) the head of a hummingbird drinking nectar from the flower. The fruit is a small, hemispherical, 1/4-1/2" capsule hidden in the remnants of the calyx. Nothing else in Illinois looks even vaguely like cardinal flowers.

Lobelia

Lobelia cardinalis

cardinal flower [Blooms: Jul-Sep]

Great blue lobelia's flower spike is 0.5-2' long, densely covered by blue-violet flowers with white stripes. individual flowers are about 1" across, the apex angled upwards, with a green, very hairy calyx with five long, narrow teeth and the bell-shaped corolla a tube that splits distally into in an upper and a lower lip, each with long white hairs on their outer surfaces. The lower lip consists of three lance-shaped, descending lobes with white patches near their bases; the upper lip has two lobes that flank on either side a cylindrical structure (five bluish stamen filaments fused with and surrounding the style) with a down-turned tip (the stigma) surrounded by brush-like anther "beards". The flower stalk and calyx are green and densely hairy. Like most lobelias, great blue lobelia contains toxic alkaloids that can produce serious symptoms; keep pets away. This species is unlikely to be confused with any other. If mystified by the flower structure, see http://iowaplants.com/flora/family/Campanulaceae/lobelia/l_siphilitica/Lobelia_siphilitica.html.

Lobelia

Lobelia siphilitica

great blue lobelia [Blooms: Aug-Oct]

Amur honeysuckle flowers occur in near-sessile pairs arising from leaf axils; there is a 2 mm long flower stalk (the thickness of a U.S. five cent coin). The corolla is about 1" long and tall, white or cream-colored, consisting of four fused, vertical upper lobes and a single lower lobe at 90° to the upper lobes; this geometry creates an opening through which protrudes five long stamens with yellow anthers and the solitary pistil with a green, knobby stigma. Outer surfaces of the flower are hairy. The fruit is a 1/4" diameter, shiny-red, spherical berry, usually in clusters of 2-4, that looks rather like a large current. The berries are mildly poisonous. The berries of amur honeysuckle are very similar in appearance and distribution to the berries of Morrow's honeysuckle (Lonicera morrowii), but the berries of the former are sessile while the berries of the latter are attached to 1/2" long pedicels. In addition, the leaves of amur honeysuckle have elongated tips while the leaf tips of Morrow's honeysuckle are relatively blunt; only amur honeysuckle has sessile flowers. Please don't plant this in your garden — too often, it escapes.

Lonicera

Lonicera maackii

amur honeysuckle [Blooms: Apr-Jun]

Morrow's honeysuckle is another invasive exotic, this one from northern Asia, a highly branched shrub 6-10' high that prefers disturbed woodlands and a strong competitor for space. Flowers arise in pairs from leaf axils on pedicels at least 1/2" long. Each flower consists of a tubular greyish-green calyx with five teeth covered with short hairs; a tubular corolla 3/4-1" long and across, initially white but becoming cream colored over time, with five long, narrow, widely-spreading lobes (four on the upper lip, one on the lower lip); five stamens with white filaments and yellow anthers; and a single, slender white style with a dome-shaped, green stigma. The fruit is a red berry 1/4" across. The berries of Morrow's honeysuckle are very similar in appearance and distribution to the berries of amur honeysuckle (Lonicera maackii), but the former are attached to 1/2" long or longer pedicels while the latter are sessile; in addition, the leaves of amur honeysuckle have elongated "drip tips" while the leaf tips of Morrow's honeysuckle are relatively blunt.

Lonicera

Lonicera morrowii

Morrow's honeysuckle [Blooms: Apr-May]

In grape honeysuckle, a short flowering stalk emerges from the tip of the stem where it emerges from the terminal pair of leaves; 2-5 whorls of flowers develop along this flowering stalk. Each flower is about 1" long. It consists of an egg-shaped, swollen, dark green ovary; a pale yellow to orange-yellow, two-lipped corolla that fades with age to orange or red; five stamens with yellow anthers; and a single style with a dome-shaped stigma. There are no hairs on the flowers. Both the stamens and the style protrude from the corolla. The ovary of fertilized flowers produces berries which are initially green but, at maturity, become globoid, orange-red to red, and about 1/4-1/2" long. Grape honeysuckle is the only honeysuckle (native or exotic) in Jackson Park that is a woody vine; it is distinctive and should be easy to recognize.

Lonicera

Lonicera reticulata

grape honeysuckle [Blooms: Jun]

Tatarian honeysuckle's flowers arise from upper leaf axils in pairs on a 3/4-1" long pedicles. Individual flowers are 3/4" (both long and across); there is a short (1/4") green calyx with five lobes; a pink to rosy-pink tubular corolla that flares to produce five narrow, spreading lobes — the middle two lobes on the upper lip of the corolla are vertical and fused at their base, the other two are spreading; the sole lobe on the lower lip is bent down. Protruding from the throat of the corolla are five stamens with white filaments and yellow anthers and a slender, white style with a green, dome-shaped stigma. The fruit is a pair of 1/4" berries that turn bright red on maturity. Of the exotic honeysuckles (amur, Morrow's, tartarian) in Jackson Park, tartarian honeysuckle is the only species that is virtually hairless and the only one with reddish (as opposed to white) flowers. Please don't plant this species in your garden — too often, it escapes.

Lonicera

Lonicera tatarica

tatarian honeysuckle [Blooms: Apr-May]

Bird's-foot trefoil produces whorls of 3-8 flowers on the end of long stalks that arise from leaf axils. Individual flowers are bright yellow (sometimes tinted with orange), about 1/2-3/4" long and across, in the standard pea-like pattern — a single vertical petal (the standard), a pair of lateral petals (the wings) and two petals perpendicular to the standard fused for about half their length (the keel). The calyx has long, light-green teeth. There are 10 stamens (of two lengths, alternating) and a single curved style, hairy at the tip. The fruit is an 1" long, purplish-brown, pea-like pod containing about two dozen seeds with the calyx at one end and a long "beak" (the remnant of the pistil) at the other.

Lotus

Lotus corniculatus

bird's-foot trefoil [Blooms: Jun-Sep]

Wild lupine is Illinois' only native lupine. The plant is small (1-2.5' tall) with light- to reddish-green stems with a grey cast from profuse short hairs (as are the leaves and leaf petioles). The flowers are blue-violet, typical pea-like flowers ~3/4" long, similar in structure to wild indigo flowers (five petals — a banner, two wings, and two keels). The fruits are 1-2" long, hairy pea-like seed pods, black when mature. The palmately-compound leaves with such a profusion of leaflets are distinctive. Wild lupine is the only known host plant for the caterpillars of the Karner Blue Butterfly (Lycaeides melissa samuelis), a federally listed endangered species.

Lupinus

Lupinus perennis

wild lupine [Blooms: May-Jun]

In common wood-rush (Luzula multiflora), culms terminate in umbels of 3-12 distinct flower clusters with green, hairless floral stalks ("rays") 1/2-3" long. The rays diverge by less than 60° from each other. (Which distinguishes this species from another Illinois species, hedgehog wood-rush (L. echinata), in which the rays diverge at greater angles.) A single flower cluster is roughly cylindrical, about 1/4" across and 1/4-1/2" long containing 6-16 flowers. Individual flowers are about 1/4" across and consist of six brownish, scaly, lance-shaped tepals 2.5-4 mm long with white, membranous margins; six stamens with bulky, pale-yellow anthers; and a single pistil with three feathery stigmas. The flowers are wind pollinated. Seed capsules are egg-shaped with a short beak and three longitudinal lobes; each lobe contains a single seed. A pair of leaf-like bracts up to 2" long is present at the base of the inflorescence. Blooms are present for only a week or 10 days in April. Common wood-rush is usually found in shaded upland areas but is present in Jackson Park in the meadow north of West Lagoon.

Luzula

Luzula multiflora

common wood-rush [Blooms: Apr]

American bugleweed flowers form in whorls of the axils of the middle and upper leaves. Individual flowers are 1/8" across, white with pinkish-purple spots, with a calyx about as long as floral tube with five teeth; the distal end of the short tubular corolla has five sharply-pointed, narrowly-triangular lobes. The two stamens with purple anthers and single style project well outside the mouth of the corolla. The fruits are four, flat-topped nutlets that form in the cup of the calyx. The deep, narrow lobes of the lower leaves are a characteristic of this species; they are not present in the other Lycopus species in Jackson Park.

Lycopus

Lycopus americanus

American bugleweed [Blooms: Jul-Sep]

Gypsywort (aka, European bugleweed) is another species native to Europe and Asia. How it came to the New World is unknown, but it has a long history in the botanical literature in Europe (back to the sixteenth century). It strongly prefers wetlands and can often be found in muds. The stem can be as much as 2.5' tall, usually unbranched, light- or yellowish-green, square in section, hairy, and finely grooved. Flowers occur in whorls in the axils of the upper leaves. Each flower is 1/8" across consisting of a green calyx with 4-5 teeth, each longer than the calyx tube, giving the mass of flowers a bristly appearance; a white tubular corolla with four apical lobes, usually with a few pink or purple spots on the lower lip; two stamens; and a style with a bifurcated tip (which can be difficult to see). The fruits are four, concave-topped nutlets cupped in the calyx. This species is known to hybridize with American bugleweed (Lycopus americanus). The medicinal properties of gypsywort are quite controversial; resist the urge to nibble.

Lycopus

Lycopus europaeus

gypsywort [Blooms: Aug-Sep]

Northern bugleweed can be up to 2.5' tall; the stem is unbranched, square in section, and light green. The leaves are opposite, 1.5-4" long and a third as wide, elliptical in outline with 5-9 coarse, sharply-pointed marginal teeth on each side of the leaf. Each pair of opposite leaves is oriented at 90° to the pairs above and below. The flowers occur in whorls in the axils of the middle and upper leaves. Individual flowers are about 1/8" long. They have a light green, very short (1 mm) calyx with 4-5 triangular teeth; a white, tubular corolla with four (or five) lobes, the uppermost notched at the tip or sometimes in two parts; two stamens with purple anthers extending just out of the corolla tube; and a style with a bifurcated tip. The fruit is four nutlets with a bumpy upper surface and a depressed center, cupped in the calyx.

Lycopus

Lycopus uniflorus

northern bugleweed [Blooms: Jul-Aug]

Fringed loosestrife is a native wildflower unrelated to the much-maligned (exotic) purple loosestrife. Flowers arise from the axils of the middle and upper leaves, held on slender, flexible pedicels up to 3" long so that the flowers commonly nod. Individual flowers are about 1" across; they have a green calyx with lance-shaped teeth behind a corolla with a reddish center and five yellow, petal-like lobes with a narrow yellow filament coming off the midline apex of most of the lobes. The five stamens have robust, tan-colored anthers and a simple white style with a tiny apical green stigma. The fruit is a shiny, green spherical capsule held cupped in the calyx. Fringed loosestrife prefers wet habitats near water or on moist hillsides.

Lysimachia

Lysimachia ciliata

fringed loosestrife [Blooms: Jun-Jul]

Winged loosestrife is a native species that has a central stem up to 3' tall, much more modest that its notorious cousin, purple loosestrife. The stem is four-sided, narrowly winged, and largely hairless; wings run along the stem but are interrupted at the leaf nodes. The inflorescence is a spike up to 1.5' long; the flowers develop singly or in pairs from the axils of bracts on the inflorescence. Each flower is pale lavender or purple and smaller than the flowers of purple loosestrife (1/4-1/2") but otherwise superficially similar — pale purple or lavender, six wrinkled petals with a medial purple stripe, six stamens. The light green, narrow calyx is about as long as the petals, has six (not five) lance-shaped teeth, and bold longitudinal stripes. The style may or may not protrude from the corolla — the flowers are distylous so the styles may either lie just inside the flower throat or protrude well outside; the style has a fuzzy, green, globular stigma. The fruit is a capsule that develops in the remnants of the calyx. Winged loosestrife prefers wet soils and is a less showy plant than purple loosestrife, but it is a native plant that plays nicely with its neighbors.

Lythrum

Lythrum alatum

winged loosestrife [Blooms: Jun-Aug]

Purple loosestrife plants are 2-5' tall. The stems branch frequently, are square in section or ridged, and are very hairy except where the stem is woody. The very showy flower spikes can be up to 20" long. Individual flowers are 1/2-1" wide that are sessile or on very short stalks; there are 5-7 (usually six) purple, wrinkled petals with a dark purple line near their base. (Imagine purple crepe paper.) The long tubular calyx is yellow-green, ridged, and hairy, with five long, narrow teeth at the distal end. Purple loosestrife is "tristylous" — it exhibits three discrete flower morphs that differ in the relative lengths of the stamens and style. Each plant bears flowers of only a single morph. Each morph has two different lengths of stamens — pistil short, stamens long AND stamens intermediate in length; pistil intermediate in length, stamens short AND long; and pistil long, stamens short AND intermediate in length. Tristyly presumably minimizes self-fertilization. Purple loosestrife is a very aggressive, invasive species which crowds out other species. Another invasive which is also called purple loosestrife, Lythrum virgatum, has similar flowers but the leaves narrow towards their base. (L. virgatum is not known to occur — yet — in Illinois.) Do not confuse purple loosestrife with the native winged loosestrife (Lythrum alatum) which has winged stems, smaller flowers (1/2"), hairless foliage, and solitary flowers in leaf axils. It's not as striking a plant as purple loosestrife, but it plays better with its neighbors.

Lythrum

Lythrum salicaria

purple loosestrife [Blooms: Jun-Sep]

False Solomon's seal's stem terminates in a flattened panicle of hairy, whitish-green stalks about 3-5" long and 2" across bearing 20-80 white flowers. The individual flowers are bright white, about 3/16" across with six narrow, spreading, strap-like tepals that are shorter than the stamens, six stamens with triangular white filaments and pale yellow or cream-colored anthers, and a single central style on top of a globose ovary. The fruit is a spherical berry, initially whitish in color, turning mottled red and later bright, translucent-red (like a currant) when ripe. It can be a bit tricky to distinguish false Solomon's seal from starry false Solomon's seal, especially early in the spring when the plants are small. Two features help: the inflorescence of false Solomon's seal is two to three the size (in linear dimensions and number of flowers) as that of starry false Solomon's seal, and the stigma of false Solomon's seal is two- or three-lobed and sessile (rests directly on the ovary), while the stigma of starry false Solomon's seal is elevated on a long style (as long as the stamens). In Jackson Park, false Solomon's seal is very tolerant of woodland habitats.

Maianthemum

Maianthemum racemosum

false Solomon's seal [Blooms: Apr-Jun]

Starry false Solomon's seal stems terminate in a 1-4" long cluster (a raceme) of up to 20 white flowers, each ~3/8" across. Individual flowers have six narrow, spoon-shaped tepals longer than the stamens, six stamens with creamy-yellow anthers, and a vase-shaped pistil with a stout style. The fruit is a 1/4" diameter berry, initially green with dark stripes, becoming bright red with maturity. The leaves of Maianthemum stellatum are much narrower than those of Maianthemum racemosum (false Solomon's seal) or Polygonatum biflorum (Solomon's seal) and has an overall appearance more like a lily than a Solomon's seal (false or smooth). It can be a bit tricky to distinguish false Solomon's seal from starry false Solomon's seal, especially early in the spring when the plants are small. Two features help: the inflorescence of false Solomon's seal is two to three the size (in both linear dimensions and number of flowers) as that of starry false Solomon's seal, and the stigma of false Solomon's seal is two- or three-lobed and sessile (rests directly on the ovary), while the stigma of starry false Solomon's seal is elevated on a long style (as long as the stamens). In Jackson Park, false Solomon's seal is very tolerant of woodland habitats; starry false Solomon's seal prefers sunnier habitats like open grasslands.

Maianthemum

Maianthemum stellatum

starry false Solomon's seal [Blooms: Apr-May]

Siberian crabapple (Malus baccata) is an exotic tree that is native to cold-temperate habits throughout Asia and has been widely planted as an ornamental in the U.S. The flowers occur in groups of 4-6. Individual flowers are 1.25" across; they have five reddish-green, lance-shaped sepals; five white, circular petals with a narrow (1-2 mm) base ("claw") attaching them to the rest of the flower; 15-20 white stamens, each 7-9 mm long with a yellow to tan anther; and five (sometimes four) green styles that are slightly longer (8-10 mm) than the stamens that have globose stigmas at their tips. The fruits (pomes) are red or yellow crabapples about 5/8" in diameter; both humans and birds find them edible.

Malus

Malus baccata

Siberian crabapple [Blooms: Apr-May]

Prairie crabapple produces clusters of 2-6 flowers on the tips of the spurs and twigs. The flowers are 1-2" across with a green, hairy, cup-shaped calyx with five narrow, triangular teeth; five white or (usually) light-pink, oval petals tapering to very narrow bases; 10-20 stamens with yellow anthers; and five robust styles. The fruits are typical crabapples about 1-1.5" across with the calyx persistent, greenish-yellow and waxy when mature; the flesh is firm but sour-tasting.

Malus

Malus ioensis

prairie crabapple [Blooms: Apr-May]

Common mallow flower stalks arise from the leaf axils. They are 1/2-1" long, attached to one to three, 1/4-1/2" wide flowers. Individual flowers have a green calyx with five pointed, triangular lobes half the length of the petals; white or pale violet squared-off petals with a shallow notch and pale violet lines; the 12-15 stamens make a bumpy, white globe around the 12-15 fused pink styles in the middle of the flower, with the inner surface of the style tips as the stigmas. The fruit is a round, flattened ovoid with radiating lines (the edges of the carpels) around a dimpled center, nestled in the remains of the calyx. Some people claim that the fruit resembles a wheel of cheese (thus one of the common names); it reminds me more of a miniature gourd. All parts of this plant are edible.

Malva

Malva neglecta

common mallow [Blooms: May-Oct]

Wild chamomile stems terminate in a daisy-like flowerhead, 1-2" across. Flowerheads consist of 10-25 white, fertile (pistillate) ray florets that tend to droop slightly and a gumdrop-shaped central mass of 250-550+ yellow disk florets with both male and female reproductive structures. Individual disk florets are tubular. Behind the flowerhead are one to three series of light green, lance-shaped bracts with membranous edges. Wild chamomile can be distinguished from similar plants like ox-eye daisy (Leucanthemum vulgare) by its multiply-pinnate, slender lobes leaves and the fact that the flowerhead is actually hollow; when crushed they produce a pleasant, fruity fragrance. Wild chamomile is closely related to pineapple weed (Matricaria discoidea) but the two can't be confused.

Matricaria

Matricaria chamomilla

wild chamomile [Blooms: May-Jun]

Pineapple-weed, unlike it's cousin wild chamomile (Matricaria chamomilla), is probably native to North America, specifically the Pacific Northwest, but has spread widely both here and in Europe. It is a small plant (up to 12" tall); the stems branch frequently. Flowerheads sit on 1/2-1.5" long flower stalks that arise from leaf axils. Each flowerhead is a gumdrop-shaped or conical mass about 8 mm across of greenish-yellow disk florets (125-535+) with four tiny lobes at the apex of the tubular corolla; there are no ray florets. The bracts behind the flowerhead have papery edges. When crushed, both the flowerheads and the foliage give off a pineapple-like fragrance. Sources differ on the biogeography of this plant. Both the USDA Plants and NatureServe Explorer websites say it is an exotic in North America; Wikipedia, the Flora of North America, World Flora Online, and the Illinois Wildflowers website say it's native to North America. Like wild chamomile, the flowerheads of pineapple-weed can be used to make a tea.

Matricaria

Matricaria discoidea

pineapple-weed [Apr-Jul]

Black medic flowerheads are ball-shaped, 1/4-3/8" across, and composed of 10-30 yellow flowers, each about 1/8" long; the flowerheads arise from leaf axils and have a 1-2" long peduncle. Individual flowers are pea-like with the upper petal (the standard) not grooved and oriented perpendicular to the lower component (the keel); the two lateral petals partially cover the keel. The flowers are very similar to those of least hop clover (Trifolium dubium), but that species has a grooved standard that is bent over to act as a hood over the keel.

Medicago

Medicago lupulina

black medic [Blooms: May-?]

White sweetclover flowers occur in spikes along 2-6" long flower stalks that arise from upper leaf axils and on the terminal upper stems. Individual flowers are small (~1/4-3/8" long), have a tubular, light green calyx with five teeth, and five white petals in the typical pea-like configuration (a single standard on the top — here, hood-like over the keel, two lateral wings, and a pair of petals fused to form a medial keel that is perpendicular to the banner). The stamens and style are hidden within the keel. Yellow sweet-clover is nearly identical to white sweet-clover (Melilotus albus) except for flower color, but blooms slightly earlier. In both yellow and white sweet-clover, the "teeth" along the distal margins of the leaflets are actually sharply-pointed extensions of the secondary (pinnate) veins. A similar extension of the central vein occurs in yellow sweet-clover but is ABSENT in white sweet-clover, permitting discrimination between the two species even when not in bloom if the vein extensions are present elsewhere on the leaflet.

Melilotus

Melilotus albus

white sweetclover [Blooms: Jun-Sep]

Yellow sweetclover flowers occur in spikes along 6" long flower stalks that arise from upper leaf axils and on the terminal upper stems. Individual flowers are small (~1/4-3/8" long), have a tubular, light green calyx with five teeth, and five yellow petals in the typical pea-like configuration (a single standard on the top (here, often hood-like over the keel), two lateral wings, and a pair of partially-fused keels in the typical pea-like configuration. The stamens and style are hidden within the keel. Yellow sweet-clover is nearly identical to white sweet-clover (Melilotus albus) except for flower color, but blooms slightly earlier. In both yellow and white sweet-clover, the "teeth" along the distal margins of the leaflets are actually sharply-pointed extensions of the secondary (pinnate) veins. A similar extension of the central vein occurs in yellow sweet-clover but is ABSENT in white sweet-clover, permitting discrimination between the two species even when not in bloom if the vein extensions are present elsewhere on the leaflet.

Melilotus

Melilotus officinalis

yellow sweetclover [Blooms: Jun-Jul]

Field mint flowers occur in whorls of about 20 above the axils of the upper leaves. Individual flowers are 1/8" long with a green calyx with small triangular lobes; a tubular, lavender, pink, or white corolla with a two-lobed upper lip and a lower lip with 0-3 lobes; four stamens protruding well beyond the tips of the flower; and a style longer than the stamens. The fruit consists of four small nutlets nestled in the flower calyx, each with a single seed. Field mint is a very widely-distributed (circumboreal) plant. Field mint is similar to Virginia bugleweed (Lycopus virginicus) in that both have flowers in whorls in the axils of paired, opposite leaves, but the latter has only white flowers in much sparser whirls with two stamens no longer than the tips of the flower. Field mint could possibly be confused with motherwort (Leonurus cardiaca) but the latter has distinctive three or five lobed angular-cleft leaves and lacks the boldly-protruding stamens of field mint. Finally, some sources (and plant ID apps) identify "Mentha canadensis" as occurring in Illinois and neighboring states. However, both ITIS (https://www.itis.gov/) and the USDA plants database (https://plants.usda.gov/) agree that the name "Mentha canadensis," often applied to this species, is invalid and a junior synonym of Mentha arvensis (field mint).

Mentha

Mentha arvensis

field mint [Blooms: Jun-Sep]

Virginia bluebells' upper stems terminate in drooping cymes of flowers. Individual flowers are 3/4-1" long with a 1/4" long, greyish-green calyx with five elliptical teeth that cups a tubular region of the corolla about 2/3 the length of the flower that in turn flares into a bell-like shape, often slightly wrinkled, with five very shallow lobes. There are five stamens with blue filaments and white anthers inside the corolla that do not emerge from the bell, the anthers reaching just past the throat; the single long, slender, white style often protrudes well beyond the margin of the bell. Virginia bluebells are pollinated by a variety of long-tongued animals including hummingbird moths (Hemaris thysbe). The fruits are four-lobed, yellow or greenish-yellow, containing four nutlets; the fruit is nestled in the flower calyx. Nothing in Jackson Park looks like Virginia bluebells; once you've identified one, you'll be confident of your ID ever afterward. For me, they are the real herald of spring, and they make me smile.

Mertensia

Mertensia virginica

Virginia bluebells [Blooms: Apr-May]

Square-stemmed monkeyflower flowers arise singly from the upper leaf axils; they are tubular and ~1" long. The calyx is light green, elongate (about 2/3" — quite large relative to the corolla), and tubular, with five sharp longitudinal ridges/wings that project into lance-like teeth; the flower pedicels are hairless and at least as long as the calyx. The corolla is usually pale blue-violet (rarely pink or white) with a two-lobed, erect upper lip (folded so the upper sides of the lobes are back to back) and a three-lobed lower lip with a patch of yellow on either side of the midline. The throat is lined with hairs and obscured by ridges in the lower lip. The seed capsules develop within the persistant calyx. The flower is quite prolific, producing 500-1000 seeds per flower. Four stamens and a single pistil are present but not visible externally. Square-stemmed monkeyflower strongly prefers moist or wet areas. The only other Illinois monkeyflower (winged monkeyflower, Mimulus alatus) apparently does not occur this far north.

Mimulus

Mimulus ringens

square-stemmed monkeyflower [Blooms: Jul-Sep]

Wild four o'clock flowers occur in clusters of 3-5, nestled in a five-lobed, saucer-shaped green bract (often with purplish tints) folded into a boxy shape; a typical calyx is absent. Instead, the flowers "petals" are a trumpet-shaped modified calyx with five notched lobes, 1/2" across and magenta in color; the 3-5 stamens protrude from the flower and have yellow anthers while the single slender pink style is even longer than the stamens, terminating in a stigma shaped like a pin head. After fertilization, the bract opens out into a whitish, pentagonal saucer (often with purplish highlights on the margins) with five radiating ridges; the rough, black, hairy seeds are suspended from the center. It is easy to mistake the mature bract for an odd flower, but a "flower" that attaches directly to the flower pedicel and lacks any trace of other flower parts (including the stamens and pistil). It's often claimed that the flowers tend to open in the late afternoon, but the wild four o'clock in Jackson Park happily open any time of day, including the morning.

Mirabilis

Mirabilis nyctaginea

wild four-o'clock [Blooms: Jun-Sep]

Twoleaf miterwort (aka, bishop's cap) is a charming little plant with a delicate flower that looks like it drifted out of a children's book. The flowers are widely spaced along the flower stalk, attached by short pedicels. Each flower is tiny (1/8" across), bell-shaped, with a short five-lobed, greenish-white calyx, and five white petals that are deeply lobed at their tips (pinnatifid), looking like a snowflake when the flower is viewed face-on. Inside the bell are 10 stamens with yellow anthers and a pair of central styles each with a yellow, crescent-shaped stigma. The fruit is a two-lobed, green capsule (like a tiny clam shell) filled with developing shiny-black seeds, all nestled in the persistant calyx. The seeds are dispersed by raindrops striking the valves of the capsule, a fitting bit of whimsy for such a marvelous plant.

Mitella

Mitella diphylla

twoleaf miterwort [Blooms: Apr-May]

Wild bergamot is a showy plant in the mint family that often occurs in dense stands in Jackson Park. Flowerheads/clusters 1-3" in diameter arise at the apex of flower stems that arise from leaf axils. Blooming begins in the center of the cluster and moves progressively toward the periphery, with the arching flowers pointing in all directions. Flowers are tubular (they remind me of baroque trumpets with embellished bells), about 1" long. They have a short green tubular calyx; a lavender or pink corolla (other mints are white, red, or purple); an awning-like upper lip beneath which protrude two stamens with brownish-purple anthers and the single style (with an unevenly bifurcated tip) significantly longer than the stamens. The 1/2" wide lower lip offers a surface where the pollinators land. The lower lip has three small lobes at its tip. Seeds develop within the persistant calyx. The very similar bee balm (Monarda didyma) has scarlet flowers. Wild bergamot is widely used as a component of herbal teas.

Monarda

Monarda fistulosa

wild bergamot [Blooms: Jul-Aug]

Spotted beebalm (aka, spotted horsemint) is a curious-looking plant 1-3' tall; it reminds me of the top of a pineapple with spotted coffee-with-cream colored flowers under the arching leaves. There are whorls of leaf-like bracts below the flowers that are white to deep pink or lavender, shorter and broader than the leaves, and invariably have smooth margins. The flowers are 3/4-1" long with a tubular calyx with five triangular teeth at the base and a cream to yellow tubular corolla with purple spots. The corolla consists of an upper lip covered with long, fine hairs on the exterior and a lower lip with three small lobes on its tip. Nestled under and paralleling the upper lip are two stamens and a style; the brown anthers and bifurcated stigma protrude beyond the tip of the lip. The fruit consists of four nutlets hidden within the persistant calyx. Spotted beebalm is unlikely to be confused with any other wildflower in Jackson Park.

Monarda

Monarda punctata

spotted beebalm [Blooms: Jul-Aug]

White mulberry is species that was introduced (from Asia) in the 1600's in an attempt to established a silkworm industry in North America; it has since escaped cultivation. Individual trees are usually either male (with staminate florets in drooping, whitish to yellow-green catkins 1-1.5" long) or female (with pistillate florets in less obvious green, erect, cylindrical catkins 1.3-3/4" long), but trees that produce both male and female florets are known. Male florets are 1/4" long with a tiny green or yellowish four-lobed calyx, four stamens, and no pistil or petals. (BTW, the pollen is released by mechanically flinging it into the air via the catapult-like stamens. See Taylor et al. 2006. Sex. Plant. Reprod. 19: 19–24.) Female florets are 1/4" long with a tiny green four-lobed calyx, a single, flattened-oval ovary with two diverging white or reddish styles and no stamens or petals. The fruit is a blackberry-like compound drupe that typically changes color from green to white, but some trees have fruit that continues maturation to red and finally to black. (Those producing black fruit are often referred to var. tartarica, but that name is invalid.) White mulberry can be usually be distinguished from black mulberry by the leaves; the underside of white mulberry leaves is invariably hairless and the top surface smooth, but the underside of red mulberry leaves is covered with small hairs and the upper surface is rough. However, white and red mulberry can hybridize, which can confuse matters significantly.

Morus

Morus alba

white mulberry [Blooms: Apr-May]

Red mulberry is a native (not introduced) species that is easily confused with white mulberry (Morus alba). Red mulberry forms substantial trees 30-60' tall; it is less common in Jackson Park that white mulberry. The trunk is short with greyish-brown bark; the bark is divided into strips by shallow vertical furrows. The leaves are alternate, 4-7+" long and 3-5" across, oval or egg-shaped in outline with serrated margins and a sharp tip. The leaves can either be a simple oval with a pointed tip or a two to three (rarely five) lobed leaf with a pointed terminal lobe; the unlobed leaves are more common. Individual trees are usually either male (with staminate florets in drooping, whitish to yellow-green catkins 3/4-2" long) or female (with pistillate florets in less obvious green, erect, cylindrical catkins 3/4" long), but trees that produce both male and female florets are known. Male florets are 1/4" long with four light green sepals, four stamens, and no pistil or petals. (BTW, the pollen is released by mechanically flinging it into the air via the catapult-like stamens.) Female florets are 1/4" long with four light-green sepals, a single, flattened-oval ovary with two white to reddish, sessile stigmas and no stamens or petals. The fruit is a blackberry-like compound drupe that typically changes color from green to red to finally purplish-black with maturation. White mulberry can be usually be distinguished from black mulberry by the leaves; the underside of white mulberry leaves is invariably hairless and the top surface smooth, but the underside of red mulberry leaves is covered with small hairs and the upper surface is rough. However, white and red mulberry hybridize, which can confuse matters significantly. Leaves may be lobed, but less commonly than in white mulberry. White mulberry can be usually be distinguished from black mulberry by the leaves; the underside of white mulberry leaves is invariably hairless and the top surface smooth, but the underside of red mulberry leaves is covered with small hairs and the upper surface is rough. However, white and red mulberry can hybridize, which can confuse matters significantly.

Morus

Morus rubra

red mulberry [Blooms: ??]

Grape hyacinth was introduced from Europe as a garden plant. The unbranched flowering scapes are green towards the base, purplish near the flowers, reaching maximum heights of 12". The leaves are all basal, 4-10" long, 3-8 mm wide, flat, hairless, and erect. The inflorescence is a terminal raceme on the scape. Individual flowers are drooping, urn-shaped with three blue sepals and three blue petals fused along their edges nearly to their tips where there are six small, rounded lobes. There are six stamens with purple anthers and a green ovary with a single style terminating in a three-lobed stigma; all are hidden well within the mouth of the urn. The fruits are three-lobed capsules, about 5 mm long and wide.

Muscari

Muscari botryoides

grape hyacinth [Blooms: Apr]

Water chickweed (aka, giant chickweed) is an exotic from Europe; it resembles a much-enlarged enlarged (potentially 1-2.5' tall vs. a few inches although the stalk sprawls) version of our common chickweeds. Flowers may occur as singletons arising from the leaf axils or clusters of a few flowers at the end of the stems. Each flower is 1/2" across; it has five fuzzy, green, oval sepals slightly shorter than the petals; five white, deeply-cleft petals that look like ten; 10 stamens with white anthers; and a green ovary with five short, arching styles. The stems and the 1" long pedicels of the flowers are both very fuzzy. The fruit is an ovoid seed capsule nestled in the persistant sepals which hangs down from the pedicel when ripe; it could easily be mistaken for a bud if you didn't notice it was pointed down.

Myosoton

Myosoton aquaticum

water chickweed [Blooms: May-Jun]

Glade mallow flowers fill the entire apex of the plant in multiple clusters (panicles). Each plant produces only male or only female flowers. Both male and female flowers are about 1/2-3/4" across with 1" long pedicels, a short, light green, tubular calyx bearing five broad teeth around the edge, and five white petals. To this general pattern, male flowers add 16-20 stamens fused basally; the free ends are separated into filaments bearing tan or pink anthers. Female flowers add to the basic flower a compound style with 6-10 white, twisted, thread-like branches. The fruits are round, fist-like clusters of wedge-shaped segments (up to 10), each containing a single seed. Glade mallow occurs in only seven states. It is listed as "vulnerable" in Illinois, Iowa, Wisconsin, and Ohio; it is "imperiled" in Indiana and Minnesota and critically imperiled in Maryland. Glade mallow prefers moist habitats. Populations in Jackson Park have been noticeably expanding over the last few years; be grateful.

Napaea

Napaea dioica

glade mallow [Blooms: Jun-Aug]

Poet's daffodil is an escapee from domestic gardens. The species is native to Central and Southern Europe; it is said to have been cultivated by the Greeks in the 3rd century BCE. The leaves are basal, blue-green, awl-shaped, up to 20" long and 1/2" wide, parallel-veined with smooth margins. The unbranched stems can get up to 1.5' tall, each with a solitary flower at their apex. The 2-3" diameter flowers have six white tepals with a yellow, crinkled central corona (often red-rimmed) in the form of a cup surrounding the reproductive organs (six stamens, only three of which are easily visible externally, and a single style with a three-lobed stigma). Fruits are rarely produced. The corona is relatively longer and bigger in diameter in wild daffodil than it is in poet's daffodil. Keep pets (and small children) away from poet's daffodil — if ingested, it induces severe vomiting.

Narcissus

Narcissus poeticus

poet's daffodil [Blooms: Apr-May]

Wild daffodil is just a daffodil that has escaped cultivation — the species is native to western Europe. Wild daffodil stems get up to 20" tall; they are unbranched with a single flower at their apex. The leaves are basal, 8-20" long, about 1/2" wide, flat, and blue-green in color. The stem and flower bud are initially aligned, but the upper part of the stem becomes plastic for a short period, deforming to reorient the upper part of the stem (and the bud) to a position perpendicular to most of the stem. Each flower consists of a conical basal section (think "calyx") with six spreading, yellow lobes (equivalent to tepals). Where the lobes/tepals bend backwards, a tubular, yellow, crinkled corona perpendicular to the tepals surrounds the reproductive structures (six stamens and a single style with a three-lobed stigma). Fruits are rarely produced. The corona is relatively longer and bigger in diameter in wild daffodil than it is in poet's daffodil. Keep pets (and small children) away from wild daffodil — if ingested, it induces severe vomiting.

Narcissus

Narcissus pseudonarcissus

wild daffodil [Blooms: Mar-May]

Catnip flowers are largely creamy-white or pink, clustered in spike-like racemes. Each flower is small (1/3-1/2") and has two unequal lips. The upper lip has two tiny lateral lobes, is smaller than the lower, and wider than long; the three-lobed lower lip is much larger, is longer than wide, has pink or purple spots, and has a frill on the lip of the middle lobe. The four stamens have anthers that are dark purple; the style protrudes just beyond the upper lip and has a bifurcated tip (the stigma). The fruit is four one-seeded nutlets nestled in the persistant calyx.

Nepeta

Nepeta cataria

catnip [Blooms: Jun-Aug]

Spatterdock is an archaic-looking water lily, and for good reason — the genus is at least 50 million years old. Single flowers are borne on the tips of stout pedicels. The buds are enclosed in three green outer sepals which reveal three underlying yellow sepals when the flower opens. An open flower is 1-3" in diameter with the opening 40-50% of that total. The yellow petals have been reduced to oblong scale-like structures inside the flower below the stamens. The large, mushroom-shaped pistil takes up most of the center of the flower the stigmatic disc visually dominating. The very numerous, oblong, truncate, ribbon-like stamens lie immediately below the large, flattened disc-like stigma; they look nothing like the delicate stamens common in most flowers. The fruit is flask-shaped, constricted below the pistil, boldly ribbed and green on the globular body; the remnant of the stigmatic disc is red-rimmed.

Nuphar

Nuphar advena

spatterdock [Blooms: Jun-Sep]

Fragrant water lily flower stalks, like the leaves, develop directly from the rhizomes. Flowers are 3-6" across; they have four greenish-white sepals that rest on the water's surface; 15-40 brilliant white (occasionally pink) petals in multiple series; 35-120 stamens with bright yellow anthers distributed around the inner circumference of tthe flower; and a central stigmatic disc on the floor of the flower at the base of the stamens. Flowers open and close daily. The fruit is 1-2" long and globoid; its stalk bends downward so the fruit develops underwater. After the tiny seeds (~1/16-1/8") are released, they float for some time, dispersed by wind and water currents, then sink to the bottom of the water body where they germinate.

Nymphaea

Nymphaea odorata

fragrant water-lily [Blooms: May-Aug]

Evening primrose — clusters of yellow flowers occur at the apex of the plant. The flowers are 1-2" across, with four 1/2-1" long green sepals strongly reflected over a long (3/4-2"), green, cylindrical floral tube (the ovary is located just above the leaf axil), four heart-shaped yellow petals, eight stamens, and a single style with an X-shaped stigma. The sepals typically remain connected (in pairs) along one edge until the flower opens. The seedpods develop within the ovary (the base of the elongate floral tube); they are hairy, urn-shaped with rounded edges, and have four or eight small lobes on the apex. The seeds are claimed to remain viable in the soil for up to 70 years. The flowers open at dusk and close early in the day. — — — There are (at least) three evening primroses in Jackson Park — common evening primrose (Oenothera biennis), northern evening primrose (Oenothera parviflora), and hairy evening primrose (Oenothera villosa). They are easily confused with each other. (Judging by the conflicts between the accounts on Illinois Wildflowers [https://www.illinoiswildflowers.info/], Minnesota Wildflowers [https://www.minnesotawildflowers.info/], and Missouri Plants [http://www.missouriplants.com/], even the experts are confused.) All three species have yellow flowers with an X-shaped stigma, reflected sepals, petals with a small notch in their apex, stems that may be red or green, and lance-shaped leaves with short, widely-spaced teeth. Northern evening primrose is distinguished by (1) the presence of a knob or ridge at the tip of each sepal which the other two species lack (2) a seed capsule with four robust, flaring lobes with rounded tips at the apex of the seed capsule, and (3) a stigma that is very robust and almost fills the opening of the flower. Northern evening primrose has green to yellowish-green sepals. Hairy evening primrose (often but not always) has (1) striped or reddish-tinged sepals (check the buds where this character is often easier to see), (2) flowers that turn orange as they begin to senesce (although the reliability of this character is uncertain), and (3) always has glandular hairs covering the ovary that have "pimple-like" bright-red bases; these red pimples may also occur on the stems. All three species are somewhat similar to prairie sundrop (O. pilosella); the latter has very hairy stems and leaves, and translucent lines that radiate from the base of the petals in the flowers.

Oenothera

Oenothera biennis

evening primrose [Blooms: Jul-Oct]

Smallflowered gaura is a spindly, usually unbranched plant that gets 2-6' fall, much of that the flower spike. The stem is round in section, light- to reddish-green, and covered with fine hairs. The leaves are alternate, 2-5" long and 1/4-1" across, lance-shaped, and sessile. The apex of the stem gives rise to a narrow spike of small flowers 1/2-2.5' long. Flowers open from the base of the spike towards the tip with relatively few open at any one time. Individual flowers are about 1/4" across. They consist of four sepals reflected back along the elongated, cylindrical, light-green or red flower stalk/ovary, four spreading white or pink petals, eight stamens, and a long style with a X-shaped (or four-lobed) stigma. The flowers are said to open in the evening and close in the morning. The seed capsules develop from the ovary; they are about 9 mm long. The flowers and flower spike of smallflowered gaura are quite distinctive and unlikely to be confused with any other species.

Oenothera

Oenothera curtiflora

smallflowered gaura [Blooms: Jul-Sep]

As the name suggests, biennial gaura is a biennial. In its first year biennial gaura develops a dense, flat basal rosette; in its second year, multiple stems shoot up from the basal rosette, branching frequently and reaching 3-7' tall. The flower spikes are 4-8" long with flowers opening from the bottom to the top. Each flower is open and airy, 1/2" long and wide, with four white or pink, spoon-shaped, petals deployed around the upper quadrant of the flower; eight long white stamens with yellow anthers and a single long white style with a yellow, X-shaped, stigma emerge at right angles to the fan of petals. Behind the petals is a red or green, hairy, tubular calyx with four sepals whose tips are reflected backwards. The fruits lie on the flower spikes behind the open flowers; they are diamond- or spindle-shaped with a flat-to-conical tip and four large ribs running longitudinally and are covered with fine hairs. Oenothera gaura is almost indistinguishable from large-flowered gaura (Oenothera filiformis, a.k.a., Gaura longiflora), but the latter has larger flowers and hairs on the stems that are curled against the stem (as opposed to straight hairs); I've not identified large-flowered gaura in Jackson Park.

Oenothera

Oenothera gaura

biennial gaura [Blooms: Jul-Sep]

Northern evening primrose flowers are 3/4-1.5" across, have four yellow, heart-shaped petals, eight yellow stamens, and a cross-shaped stigma on a modest style; the stamens are as long or longer than the petals and the stigma is nearly fills the floral opening. At the base of the flower are four sepals 1/2-1" long, that bend back along the 3/4-1.5" long floral tube as the flower develops with pairs of sepals attached along one edge until the flower opens. Only northern evening primrose with a distinct ridge or knob near the tips of the sepals. The seed capsule develops from the ovary; it is 3/4-1.5" long, cylindrical but tapering slightly towards the tip, with four robust, flaring lobes at the tip. — — — There are (at least) three evening primroses in Jackson Park — common evening primrose (Oenothera biennis), northern evening primrose (Oenothera parviflora), and hairy evening primrose (Oenothera villosa). They are easily confused with each other. (Judging by the conflicts between the accounts on Illinois Wildflowers [https://www.illinoiswildflowers.info/], Minnesota Wildflowers [https://www.minnesotawildflowers.info/], and Missouri Plants [http://www.missouriplants.com/], even the experts are confused.) All three species have yellow flowers with an X-shaped stigma, reflected sepals, petals with a small notch in their apex, stems that may be red or green, and lance-shaped leaves with short, widely-spaced teeth. Northern evening primrose is distinguished by (1) the presence of a knob or ridge at the tip of each sepal which the other two species lack (2) a seed capsule with four robust, flaring lobes with rounded tips at the apex of the seed capsule, and (3) a stigma that is very robust and almost fills the opening of the flower. Northern evening primrose has green to yellowish-green sepals and is the only one of the three evening primroses to (sometimes) have reddish color on some or all of the midvein of the leaves. Hairy evening primrose (often but not always) has (1) striped or reddish-tinged sepals (check the buds where this character is often easier to see), (2) flowers that turn orange as they begin to senesce (although the reliability of this character is uncertain), and (3) always has glandular hairs covering the ovary that have "pimple-like" bright-red bases; these red pimples may also occur on the stems. All three species are somewhat similar to prairie sundrop (O. pilosella); the latter has very hairy stems and leaves, and translucent lines that radiate from the base of the petals in the flowers.

Oenothera

Oenothera parviflora

northern evening primrose [Blooms: Jun-Jul]

Prairie sundrop is similar to evening primrose (O. biennis) but more delicate and only about 2' tall. The flowers are ~2" across, pale golden-yellow, with translucent lines that radiate from the petals' bases. The flower is attached to a 1/2-1" long floral tube whose base is the ovary, nestled in a leaf axil. The floral tube is covered by four hairy sepals; the four petals are heart-shaped; the stamens are long, yellow, with large yellow anthers; the style extends well beyond the stamens and has a large, X-shaped stigma. Each flower lasts only about a day. The fruits form from the ovary which often have four prominat wings. The fruits are ~1/2" long, four-angled or ridged, club-shaped, with four internal chambers filled with 1 mm long seeds.

Oenothera

Oenothera pilosella

prairie sundrop [Blooms: Jun]

Hairy evening primrose produves an elongating spike of flowers arises from the apex of the stem; flowers bloom near the tip while older flowers and seed capsules develop below. Individual flowers are 3/4-1.5" across; they sit on a long floral tube with the ovary at its base (attached to a leaf axil). The flowers have four yellow, heart-shaped petals, eight yellow stamens, and a cross-shaped stigma on a modest style; at the base of the flower are four sepals 3/8-3/4" long, reflected back along the floral tube as the flower develops with pairs of sepals attached along one edge until the flower opens. The sepals are often red-striped or red-tinged. Note the long, hairy floral tube below the sepals, the reddish stem, and glandular hairs with red bases on the ovary. The seed capsule develops from the ovary; it is up to 1.75" long, cylindrical but tapering slightly towards the tip, with four tiny lobes at the tip. — — — There are (at least) three evening primroses in Jackson Park — common evening primrose (Oenothera biennis), northern evening primrose (Oenothera parviflora), and hairy evening primrose (Oenothera villosa). They are easily confused with each other. (Judging by the conflicts between the accounts on Illinois Wildflowers [https://www.illinoiswildflowers.info/], Minnesota Wildflowers [https://www.minnesotawildflowers.info/], and Missouri Plants [http://www.missouriplants.com/], even the experts are confused.) All three species have yellow flowers with an X-shaped stigma, reflected sepals, petals with a small notch in their apex, stems that may be red or green, and lance-shaped leaves with short, widely-spaced teeth. Northern evening primrose is distinguished by (1) the presence of a knob or ridge at the tip of each sepal which the other two species lack (2) a seed capsule with four robust, flaring lobes with rounded tips at the apex of the seed capsule, and (3) a stigma that is very robust and almost fills the opening of the flower. Northern evening primrose has green to yellowish-green sepals. Hairy evening primrose (often but not always) has (1) striped or reddish-tinged sepals (check the buds where this character is often easier to see), (2) flowers that turn orange as they begin to senesce (although the reliability of this character is uncertain), and (3) always has glandular hairs covering the ovary that have "pimple-like" bright-red bases; these red pimples may also occur on the stems. All three species are somewhat similar to prairie sundrop (O. pilosella); the latter has very hairy stems and leaves, and translucent lines that radiate from the base of the petals in the flowers.

Oenothera

Oenothera villosa

hairy evening primrose [Blooms: Aug-Oct]

Eastern prickly pear is the commonest of three prickly pears native to Illinois, all quite rare. Eastern prickly pear can grow to be as much as 2' tall but Jackson Park specimens rarely exceed 6". Flowers are 2-3" across consisting of numerous yellow, satiny tepals, the innermost layer with reddish-orange highlights towards the tepals bases, 50-1500 stamens with pale yellow anthers, and a single style topped with a ring of six fleshy, white stigmas. Each flower lasts a single day. Fruits are initially green but turn reddish-brown when mature; they are 1-2" long, less than 1" in diameter, and concave on the top.

Opuntia

Opuntia humifusa

Eastern prickly-pear [Blooms: Jun-Jul]

French grass flowers are 1/4" long, pea-like, with a short, green, tubular calyx with five teeth, and five blue, purple, or white petals — a single upright banner, two forward-projecting wings, and two closely-appressed petals that make up the keel (largely hidden by the wings). Ten stamens and the style are nestled inside the keel. Seedpods are about 1/2" long with a stout, pointed "beak."

Orbexilum

Orbexilum onobrychis

French-grass [Blooms: Jun-Jul]

Star of Bethlehem's unopened flower buds bear alternating green and white triangles on the enclosing tepals that make the species easy to ID even before the flowers open. Flowers are about 3/4" across with six tepals, white on the top surface and the margins of the underside, green along the centerline of the tepal's underside; six stamens with yellow to brownish anthers whose filaments are flattened to form a visually-striking picket fence topped by sharp points; and a single pistil with a six-ridged yellow ovary and a single yellowish-green style. The fruits are three-celled with six exterior ridges, initially looking like the bottom of a miniature green bell pepper. The flowers produce lots of nectar; they tend to open before noon and close before sunset (or much earlier on cloudy days). Star of Bethlehem is an escapee from cultivation and is competitively quite aggressive. This species produces toxic cardiac glycosides throughout the plant but especially in the flowers and bulbs; it has been reported to have poisoned unwary sheep.

Ornithogalum

Ornithogalum umbellatum

star of Bethlehem [Blooms: May]

Aniseroot tends to be an understory plant, 1-2.5' tall. Individual flowers are tiny (1/8"), grouped in distinct compound umbels, each with several narrow, lance-shaped bracts with hairy margins at the base of the umbel. The flowers have a tiny green calyx without sepals, five white petals with incurled tips, five stamens with white anthers, and a pistil with a divided white style (longer than the petals — about 2 mm). The fruit is a hairy, narrow, arched seedpod about 1" long; the two styles (and, less commonly, petals and stamens) persist at the tip of the seedpod for part of the maturation. Aniseroot is very similar to sweet cecily (Osmorhiza claytonii), but aniseroot has more flowers (8-16) in each umbel than does sweet cecily (4-7) and the two styles in the flower are short and dumpy (shorter than the petals) in sweet cicely and much longer (longer than the petals) in aniseroot. The stems and stalks (except the umbel stalks) are densely covered with fine, short hairs or no hairs in aniseroot, long, spreading hairs in sweet cecily. The crushed leaflets smell like — surprise! — anise in aniseroot.

Osmorhiza

Osmorhiza longistylis

aniseroot [Blooms: Apr – Jun]

Hop hornbeam (aka, ironwood) flowers are in the form of catkins, with separate male and female inflorescences. Male (staminate) catkins are 1-2" long, narrowly cylindrical, often occurring in groups of three; male flowers have three stamens. Female (pistillate) catkins are 1/2" long and stubby, occurring singly at the tips of branches; individual flowers consist of a basal, green bract and two red, thread-like styles. The flowers are wind-pollinated. The fruit is 1.5-2.5" long and 3/4-1" wide, superficially similar to the fruit of hops vines (Humulus lupulus), with flattened, spindle-shaped nutlets 5-8 mm long hidden inside yellowish, papery, inflated sacs 1/3-1" long.

Ostrya

Ostrya virginiana

hop hornbeam [Blooms: Apr-May]

The yellow-flowered wood-sorrels in general (of which yellow wood sorrel is one) are difficult to distinguish and have given rise to much taxonomic confusion. (I.e., it's not just us; even the pros have problems. Read on.) Flowers are 3/8-1/2" across; they have five light green sepals, shorter than the petals, five yellow petals with rounded tips, ten stamens with yellow anthers, and a single pistil with five styles fused except at their tips. These flowers often have a ring of red lines around the throat (like yet another species, O. illinoensis). The seed capsules are 1/4-1/2" long, banana-shaped, erect, hairy, and five-sided; the capsules use explosive seed dispersal (like jewelweed and wild geranium) to scatter the contained seeds. This species is very similar to another yellow wood sorrel, Oxalis dillenii; see https://www.minnesotawildflowers.info/flower/yellow-wood-sorrel for details on how to distinguish the two. (A good hand lens or a microscope are required.)

Oxalis

Oxalis stricta

yellow wood-sorrel [Blooms: May-Sep]

Cowbane is a spindly, sparse plant 2-5' tall. At their apex, the stems produce shallowly dome-shaped compound umbels 3-5" across of 10-25 umbelletes of 10-20 small white flowers each. Individual flowers are about 3 mm across; each has a short calyx, five white petals with notched tips, five stamens with white anthers, and a central greenish or white ovary with two styles. The fruit is a elongate (1/4" long), flattened oval with wings on the flattened edges, longitudinal stripes/ribs and, initially, with the remnants of the two styles at their tips; when mature it splits, releasing two seeds. Cowbane prefers wet soils. As you might suspect from the name, it is toxic if eaten.

Oxypolis

Oxypolis rigidior

cowbane [Blooms: May-June]

Butterweed stems produce a flattened panicle of flowers about 6" across with a single series of bracts (phyllaries) surrounding the base of the flowerhead. Individual flowerheads are 1/2" across with 5-15 yellow, narrowly-oblong pistillate ray florets and 35-50+ yellow, tubular disk florets with five apical lobes a single style that extends just past the anthers, and five stamens attached to the inside of the tubular corolla; the disk is 4-5 mm across. The fruit is a single, five-angled seed with a tuft of white hairs (like a dandelion). Butterweed contains toxic compounds (probably pyrrolizidine alkaloids) which deter most mammalian herbivores (although some domestic herbivores do eat it and suffer the consequences). According to ILW, butterweed was typically restricted to southern Illinois, with a few recent occurrences in central Illinois. Apparently, it has now made its way to Cook County. Butterweed (Packera glabella), balsam ragwort (Packera paupercula), and prairie ragwort (Packera plattensis) are easy to confuse — all bloom in the late spring/early summer and all are weedy-looking plants with yellow/golden-yellow, daisy-like flowers. With one exception, the flowers don't help to distinguish them; however, the petals of butterweed, seen from behind, have a strap-shaped blade with 2-3 teeth at the distal end and a narrow tube (the corolla tube) about a quarter the length of the strap connecting the strap to the rest of the flower (not present in the ragworts). In general, you'll need to look carefully at the leaf shape and presence/absence and quantity of wooly fine white hairs on the leaves and stems. Butterweed has large (10" long) basal leaves; the leaves are pinnatifid with multiple semicircular lobes and a circular terminal lobe. Balsam ragwort (Packera paupercula) basal leaves are no longer than 3", the flowerheads have 0, 8, or 13 ray florets, the phyllaries behind the flowerhead are purple-tipped, and wooly hairs are usually found in the leaf axils. Prairie ragwort (Packera plattensis) is extensively covered with white wooly hairs on the stems, leaves, leaf axils, and on the phyllaries behind the flowerheads.

Packera

Packera glabella

butterweed [Blooms: May-Jun]

Balsam ragwort flowerheads are 1/2-3/4" across 8 or 13 (rarely, 0) pale yellow ray florets and 50-65+ golden-yellow disk florets. Both disk and ray florets are perfect (i.e., have both male and female reproductive structures). The disk florets are tubular with five lobes at their apex; they have a single style and five stamens. At the base of each flowerhead is a single series of bracts (phyllaries); the phyllaries are light green, fading to pale purple at their tips. Butterweed (Packera glabella), balsam ragwort (Packera paupercula), and prairie ragwort (Packera plattensis) are easy to confuse — all boom in the late spring/early summer and all are weedy-looking plants with yellow/golden-yellow, daisy-like flowers. The flowers don't help to distinguish them; you'll need to look carefully at the leaf shape and presence/absence and quantity of wooly fine white hairs on the leaves and stems. Butterweed has large (10" long) basal leaves; the leaves are pinnatifid with multiple semicircular lobes and a circular terminal lobe. Balsam ragwort (Packera paupercula) basal leaves are no longer than 3", the flowerheads have 0, 8, or 13 ray florets, the phyllaries behind the flowerhead are purple-tipped, and wooly hairs are usually found in the leaf axils. Prairie ragwort (Packera plattensis) is extensively covered with white wooly hairs on the stems, leaves, leaf axils, and on the phyllaries behind the flowerheads.

Packera

Packera paupercula

balsam ragwort [Blooms: Apr-May]

Prairie ragworts stems and leaves are covered with cobwebby hairs and the leaf blade with felt-like hairs. Cobwebby hairs also cover the flower stems which bear a cluster of 3-12 flowerheads at their apex. Individual flowerheads are 1/2-3/4" across, with 7-12 yellow ray florets and 60-70+ orangish-yellow disk florets; both ray and disk florets have a single style and five stamens. The central disk is about 8 mm across. The fruit is a single seed suspended from a tuft of white hairs (like a dandelion). The underside of the flowerhead is covered by a single series of light green bracts (phyllaries) also covered with cobwebby hairs. Prairie ragwort can be usually distinguished from other Packera spp. by the extensive cobwebby hairs on the stems and leaves. Butterweed (Packera glabella), balsam ragwort (Packera paupercula), and prairie ragwort (Packera plattensis) are easy to confuse — all bloom in the late spring/early summer and all are weedy-looking plants with yellow/golden-yellow, daisy-like flowers. The flowers don't help to distinguish them; you'll need to look carefully at the leaf shape and presence/absence and quantity of wooly fine white hairs on the leaves and stems. Butterweed has large (10" long) basal leaves; the leaves are pinnatifid with multiple semicircular lobes and a circular terminal lobe. Balsam ragwort (Packera paupercula) basal leaves are no longer than 3", the flowerheads have 0, 8, or 13 ray florets, the phyllaries behind the flowerhead are purple-tipped, and wooly hairs are usually found in the leaf axils. Prairie ragwort (Packera plattensis) is extensively covered with white wooly hairs on the stems, leaves, leaf axils, and on the phyllaries behind the flowerheads.

Packera

Packera plattensis

prairie ragwort [Blooms: Apr-Jun]

Mature wild quinine plants are 2-3' tall. On the flowering stalks (and the side branches) are flat topped clusters of white, button-like flowerheads about 3/8" across. (The Illinois Wildflowers website considers them "similar to a head of cauliflower.") Flowerheads are composed of 15-35 disk florets, often with blackish, club-like stamens poking out; the 5-6 ray florets bear a tiny, cup-shaped petal and a pistil with a bifurcated stigma. No other wildflower in Illinois has flowerheads anything like wild quinine; common and widespread in Jackson Park.

Parthenium

Parthenium integrifolium

wild quinine [Blooms: May-Aug]

Virginia creeper produces panicles of 80-150 flowers opposite leaf nodes; the panicles are broader than long and have a distinct central axis. Individual flowers are 1/4" across, green, with five petals, five white stamens with yellow anthers, and a single stout, cone-shaped style. Flowers may have only stamens, only pistils, or both pistils and stamens. The petals have a raised margin (less so than woodbine) and are reflected backwards around the flower stalk. The fruit is a fleshy berry that is initially green but becomes blue-black with maturation; the flower stalks become orange-red or red as the fruit matures. The clusters of the fruit are reminiscent of a bunch of grapes. Opposite the leaf nodes are tendrils with as many as 10 branches; the tendrils end in distinct (adhesive) pads. Virginia creeper plants growing on trees produce aerial roots with a distinct "beard" of rootlets. Woodbine (Parthenocissus vitacea) also has palmate leaves with five leaflets, very similar to Virginia creeper (P. quinquefolia), but lacks the distinctive "bearded" aerial roots with short rootlets that are present in Virginia creeper. Opposite the base of the leaf petiole on the stem, woodbine produces a thin filament that branches 2-3 times, anchoring the vine by twining around objects. In Virginia creeper, the equivalent filaments are stouter, branch up to ten times, and end in robust, egg-shaped pads that attach to the substrate. The inflorescence of woodbine lacks a central axis; the inflorescence of Virginia creeper has a distinct central axis. Wikipedia (https://en.wikipedia.org/wiki/Parthenocissus_inserta) lists other differences between the two species. Illinois Wildflowers, USDA Plants, and and World Flora Online consider the two species to be one; Minnesota Wildflowers considers them to be separate and distinct. Flora of North America indicates the correct scientific name for woodbine is Parthenocissus vitacea (not P. inserta), as does ITIS and MissouriPlants.com, implying that woodbine and Virginia creeper are distinct species. Both woodbine and Virginia creeper have 40 chromosomes. Lu et al.'s (2012, 2023) molecular and morphological analyses indicate that woodbine and Virginia creeper are very closely related but distinct species and I'll consider that to be correct here.

Parthenocissus

Parthenocissus quinquefolia

Virginia creeper [Blooms: June]

Boston ivy is an exotic introduced from Asia; it is a woody vine up to 50' long (with occasional branches) that grows on or over fences, walls, concrete, masonry, and trees. The lower stems are woody and produce small brown rootlets to adhere to surfaces; upper stems are (also) hairless, green to orange-red in color, with branched tendrils that have adhesive pads at their tips. Leaves are alternate, 6" long and across exclusive of the long, slender petioles, palmately tri-lobed with undulating or crenate margins. Cymes of flowers lacking a distinct central axis arise from the leaf axils; the cymes are 4" in both dimensions. Individual flowers are 1/4" across; they have five yellowish-green petals, five stamens with yellow anthers, and a single style. Fertilized flowers produce berries 3/8" across. When mature the berries are dark blue with a whitish bloom, usually hidden beneath the leaves; the flower stalks are yellow- or brownish-green or a dull orange-red.

Parthenocissus

Parthenocissus tricuspidata

Boston ivy [Blooms: ??]

Woodbine is a woody vine that usually uses trees as a substrate; the vine can be as much as 60' long. The stem is initially green and hairless; as it matures it becomes woody and develops a reddish- or grey-brown color. The leaves are alternate, palmately compound, usually with five (rarely 4 or 7) leaflets that are about 5" long and 2.5" wide with coarse marginal teeth, shiny-green when young but getting duller with age; the compound leaf has a slender 6-8" long petiole. Three- to six-inch-long clusters of 10-75 flowers arise from the main vines opposite the leaves; the clusters have two main branches and multiply-branched flower stalks with no clear central stem. Individual flowers are inconspicuous, 1/4" across with five yellowish green petals with narrow margins perpendicular to the plane of the petal and a pointed, curled tip; the petals are initially spreading but later become reflected backwards. In the center of the flower are five pale red stamens with creamy white or purple anthers, a reddish ovary, and a single white, stubby, conical style. The fruits are round blue-black berries 3/8" across that are reminiscent of grapes in a cluster with red, branched flower stalks; each berry contains four seeds. Woodbine has palmate leaves with five leaflets, very similar to Virginia creeper (Parthenocissus quinquefolia), but lacks the distinctive aerial roots "bearded" with short tendrils that are present in Virginia creeper. Opposite the base of the leaf petiole on the stem, woodbine produces a thin filament that branches 2-3 times, anchoring the vine by twining around objects. In Virginia creeper, the equivalent filaments are stouter, branch up to 10 times, and end in robust, egg-shaped pads that attach to the substrate. The inflorescence of woodbine lacks a central axis; the inflorescence of Virginia has a distinct central axis. Wikipedia (https://en.wikipedia.org/wiki/Parthenocissus_inserta) lists other differences between the two species. Illinois Wildflowers, USDA Plants, and and World Flora Online consider the two species to be one; Minnesota Wildflowers considers them to be separate and distinct. Flora of North America indicates the correct scientific name for woodbine is Parthenocissus vitacea (not P. inserta), as does ITIS and MissouriPlants.com, implying that woodbine and Virginia creeper are distinct species. Both woodbine and Virginia creeper have 40 chromosomes. Lu et al.'s (2012, 2023) molecular and morphological analyses indicate that woodbine and Virginia creeper are very closely related but are distinct species, and I'll consider that to be correct here.

Parthenocissus

Parthenocissus vitacea

woodbine [Blooms: ??]

Wild parsnip is an exotic plant, native to Eurasia, in the carrot family (Apiaceae); it produces flat umbels of flowers (like Queen Anne's lace, except yellow). This is the wild version of the domestic parsnip. The compound umbels are 3-8' across, flat topped, with 15-25 umbellets; each umbellet includes 15-35 1/8" yellow flowers borne on 3/8" long pedicels. Individual flowers have five very short, yellow petals, initially curled inward, but later the petals reverse curvature and curl outwards; there are also five yellow stamens and two styles that arise from an ovary with a swollen, greenish-yellow nectar pad. The fruits are 1/4" long flat, oval, coin-like discs; when mature the disk is brown and the edges of the disk are winged.

Pastinaca

Pastinaca sativa

wild parsnip [Blooms: May-Jun]

Wood betony's numerous yellow (less commonly, reddish brown) flowers arise from a spike (raceme) at the apex of the stem; the blooms open in a wave from the base of the spike to its tip. The flowers tend to be twisted clockwise around their long axis by about 30° so that, viewed from above, the flower spike looks like a pinwheel. Individual flowers are 1/2-1" long, tubular, with a hood-like upper lip that curves down into two small "teeth" or "fangs" at its tip (a distinguishing character of this species) and a paler or white three-lobed lower lip that functions as a landing pad for pollinators. The four stamens are hidden under the upper lip of the corolla; they are of two lengths with light yellow anthers. The single style is also largely hidden under the upper corolla lip, although the tip of the style may protrude; the stigma looks like the head of a common pin. The fruit is a 1/2" long, angular capsule reminiscent of a shoe tree (as in footwear, not plants) that is initially green, turning brown as it matures.

Pedicularis

Pedicularis canadensis

wood betony [Blooms: Apr-Jun]

Calico penstemon (aka, long-sepaled penstemon) is a typical penstemon/beardtongue — 1-3' tall with an unbranched stem and a panicle of flowers at the apex of the stem. Flowers are about 1" long, with a calyx with five long (5-12 mm), narrow (1-2 mm) lobes, a tubular corolla with two upper lobes and three lower lobes on the aperture, and four stamens and a single style, all enclosed by the corolla. The corolla's exterior is light purple or light violet and covered in fine hairs; the interior of the corolla is white and smooth, without ridges. The lobes on the lower lip of the corolla do not protrude beyond the lobes of the upper lip. Calico penstemon is fairly rare in Jackson Park.

Penstemon

Penstemon calycosus

calico penstemon [Blooms: Jun-Jul]

Foxglove beardtongue's inflorescence consists of 3-6 pairs of panicles at the apex of the stems. Individual flowers are white or (less often) pink with a green or maroon calyx, five narrowly triangular lobes, and a tubular corolla that flares abruptly distal to the calyx. The corolla's aperture bears five lobes (two above on the upper lip, three below on the lower lip) with pink or purple nectar guides inside the tube. The filament of a sterile stamen (a "staminode") bearing sparse yellow hairs runs along the midline of the lower half of the corolla, while the filaments of the other four stamens wrap around the inside of the corolla like ribs in a ribcage, with the black anthers positioned on either side of the midline of the upper corolla. A single style runs along the upper midline between the black anthers to emerge between the two upper aperture lobes. The fruit is a bullet-shaped capsule about 1/2" long nestled in the persistant calyx. The calyx, flower stalks, and the flowers themselves are densely covered by glandular hairs; the main stems and leaves are hairless. Foxglove beardtongue is ubiquitous in Jackson Park.

Penstemon

Penstemon digitalis

foxglove beardtongue [Blooms: May-Jul]

Slender beardtongue (aka, lilac penstemon) is another beardtongue/penstemon that is uncommon in Jackson Park. The stems are unbranched, green or purple, and may or may not bear hairs. There are both basal and stem leaves. The basal and lower stem leaves are 1-3" long and 1/2" wide, variable in shape and leaf margins; the stem leaves are smaller and minutely toothed. Individual flowers are pinkish, purple, or pale violet, about 3/4" long; they are comprised of a green calyx with five triangular lobes and a tubular corolla that is abruptly inflated in the more distal two thirds of the flower. The lower lip of the corolla has three lobes that extend down and out from the aperture the upper lip has two smaller, erect lobes. The interior of the corolla is white with several dark purple lines that act as nectar guides. The filament of a sterile stamen (a "staminode") bearing sparse yellow hairs runs along the midline of the lower half of the corolla, while the filaments of the other four stamens wrap around the inside of the corolla like ribs in a ribcage, with the black anthers positioned on either side of the midline of the upper corolla. A single style runs along the upper midline between the black anthers. The fruit is a more or less bullet-shaped capsule nestled in the persistant calyx. The calyx, flowers, and flower stalks are all covered with glandular hairs; the stems and leaves are not.

Penstemon

Penstemon gracilis

slender beardtongue [Blooms: Jun-Jul]

Large-flowered penstemon flowers develop in the axils of the stem leaves in pairs. (Occasionally a triplet will arise.) Individual flowers are up to 2" long, pale lavender or pink, tubular, sightly flattened vertically but flaring at the aperture, with a two-lobed upper lip and 3-lobed lower lip with purple lines on the interior. The bluish-green calyx has five teeth. A distinct longitudinal ridge runs along the upper surface of the corolla, intersecting the aperture between the two upper lobes. A white style with a tiny stigma runs along the inside of the corolla under the longitudinal ridge and protrudes from the throat. The four fertile stamens are recessed, with their filaments wrapped around the inside of the corolla like a ribcage and the anthers on either side of the dorsal midline; the fifth (sterile) stamen runs along the lower midline and ends in a recurved or coiled tip with a prominent pad bearing short, brilliant-yellow hairs. The fruit is a teardrop-shaped seed pod nestled in the remains of the calyx. Large-flowered penstemon prefers poorer but well-drained soils with significant rocky material or sand. This species is officially listed as "endangered" in Illinois.

Penstemon

Penstemon grandiflorus

large-flowered penstemon [Blooms: May-Jul]

Hairy beardtongue is 1-2.5' tall and blatantly hairy — backlit plants seen from a distance show a white nimbus around the stems. The flowers are slender, lavender colored, with white lips; the aperture of the flower is nearly occluded by the arched lower lip. Like the other beardtongues/penstemons the tubular flowers have an upper and lower lip have a total of five lobes (two above, three below). The calyx, flower stems, and the flowers themselves are densely covered by glandular hairs; the stems are densely covered with fine white hairs. The stem leaves are pointed, triangular with toothed margins, and occur in opposite pairs; the leaf pairs are oriented at 90° to the pairs above and below them on the stem.

Penstemon

Penstemon hirsutus

hairy beardtongue [Blooms: May-Jul]

Pale beardtongue stems terminate in a 4-10" long panicle of flowers that is longer than broad. Flowers are 3/4" long consisting of a short, green calyx with five teeth, a tubular, white corolla similar to that of other penstemons/beardtongues, four fertile stamens with brown anthers, a bright yellow "beard" on the lower lip (as in hairy beardtongue), and a single style. The upper lip of the corolla has the usual two erect lobes, but the lower lip has three rounded lobes that project forward well beyond the margin of the upper lip. The outer surfaces of the flowers and flower stalks are covered with hairs. The throat of the corolla's lower surface has three thin purple veins, a narrow patch of long, bright yellow hairs, and a pair of low ridges/grooves, one on either side of the midline. The fruit is an egg-shaped capsule 1/4" long nestled in the persistent calyx. Both pale beardtongue and foxglove beardtongue (Penstemon digitalis) have white flowers and might be confused. However, the flowers of pale beardtongue are smaller, the flowers have two distinct ridges on the interior of the lower half of the corolla, and the three lobes on the lower lip are parallel to the floor of the corolla and extend well beyond the upper lip. None of these traits are present in foxglove beardtongue. In Jackson Park, pale beardtongue is less common than hairy beardtongue and much less common that foxglove beardtongue.

Penstemon

Penstemon pallidus

pale beardtongue [Blooms: May-Jun]

Ditch stonecrop is native to North America; its range includes the majority of the states in the U.S. and the provinces in Canada. It is a small (1-2' tall) plant with green or red stems, usually unbranched. Cymes of flowers 1-3" across arise from the upper stems, each cyme with 2-4 spreading flowering stalks; flowers are restricted to only one side of the flower stalks. Individual 1/4" flowers are yellowish-green to white, have five spreading, green sepals, ten stamens with cream-colored or yellow-orange anthers, and five beaked carpels, each with a single style and a green stigma; petals are completely absent. (The carpels look rather like a teapot with no handle and a very wide spout, or like a "duck" wine decanter. Look it up.) The carpels become the seed capsules; they turn bright red when mature. Ditch stonecrop prefers wet habitats (like ditches). It is completely unrelated to biting stonecrop (Sedum acre).

Penthorum

Penthorum sedoides

ditch stonecrop [Blooms: Aug-?]

At the apex of the stems and branches of wild dill are compound umbels of small white flowers; the umbels are about 6" across and have 12 umbellets that are widely spaced from each other. An umbellet is about 1" across and contains 7-21 flowers. Individua flowers are about 3 mm (1/8") across, consisting of 5 small, triangular, green sepals; 5 petals, each notched at the tip; (ideally) 5 stamens with white anthers; and a hairless ovary formed from two fused carpels, each with a short style. The stamens are fragile and often fall off, so there may be less than five stamens present. The fruit is an elongated schizocarp 3-5 mm long with a longitudinal groove that splits to release laterally flattened, wingless, brown to black seeds. Often, the remnants of the styles persist at the apex of the fruit.

Perideridia

Perideridia americana

wild dill [Blooms: Jun]

Waterpepper is a rather spare plant, 1-2' tall which needs close observation to be appreciated. 2-7" long spikes of minute flowers, only a few of which are open at any one time, terminate the upper stems; the flower spikes often nod or droop. Each greenish-white flower is ~1/8" long with five tepals covered with glandular pits (see below), green towards the base, brilliant white at the tips, 4-6 white stamens, and 2-3 white styles. The flowers never open very far. P. hydropiper is distinguished by (usually) reddish stems and the presence of tiny glandular pits (often pale yellow or brown, and only visible with magnification) on the greenish portions of the tepals. Cultivated varieties of waterpepper have been eaten in Japan and Europe, but the wild form produces a variety of oils that can cause skin (including the oral mucosa) irritation and swelling.

Persicaria

Persicaria hydropiper

waterpepper [Blooms: Aug-Sep]

Pale smartweed is a very tall smartweed (2.5-4') characterized by long, dense, drooping, whitish flower clusters and the absence of bristles on the leaf sheaths (ocreae). Stems terminate in drooping flower spikes 2-8" long, densely packed with small (1/8" long) flowers. Individual flowers have 4-5 greenish-white to pinkish tepals, 5-6 stamens with pink anthers and two styles. Because the flowers open only at their tips, the reproductive structures are difficult to observe. After fertilization, a three-angled seed, 2 mm across, develops nestled in the tepals. This is the largest smartweed that occurs in Illinois. Pale smartweed prefers wet soils (e.g., the shores of water bodies). Pale smartweed is similar to Pennsylvania smartweed (Persicaria pennsylvanica) but that plant has erect, cylindrical flower spikes and the flowers are pink or reddish.

Persicaria

Persicaria lapathifolia

pale smartweed [Blooms: Jul-Oct]

Creeping smartweed is another weedy exotic, but its charm increases as you look closer. The flower spikes are 1.5" long and <1/4" wide; they are covered with tiny (~1/8" long) flowers with five pink tepals, only a few of which are open at any one time. (Petals are absent.) There are five stamens with pink or yellow anthers and three styles hidden within the flower; they are visible only with difficulty. At the base of each flower is a small membranous sheath with bristles as long or longer than the flowers (not present on all flowers). After fertilization, a three-angled seed that tapers to a point on each end develops nestled in the tepals. This is an Asian species that was introduced to North America around 1910 near Philadelphia and reached Illinois in the 1940's; it strongly prefers wet soils. Creeping smartweed resembles lady's-thumb (Persicaria maculosa), but creeping smartweed's sprawling habit and the long bristles associated with the flowers are distinctive.

Persicaria

Persicaria longiseta

creeping smartweed [Blooms: May-Oct]

Lady's-thumb is an exotic, native to Europe, but has a long history in North America — it was first reported from the Great Lakes in 1843. Flower spikes (racemes) are 1/2-1.5" long and densely covered with tiny (1/8" long) pinkish-white flowers; flower color is quite variable, even within a single flower spike. The flowers are "shy" and often open only at the tips of the 4 or 5 sepals (there are no petals); both the six stamens and the single style (divided into three towards the distal end) remain hidden. Seeds are black; they develop singly within the persistent sepals and remain largely hidden by the sepals; they can be found on flower heads still blooming. Lady's-thumb prefers wet habitats.

Persicaria

Persicaria maculosa

lady's-thumb [Blooms: Jun-Sep]

Pennsylvania smartweed flower spikes are 3/4-2" long, distinctly cylindrical with a blunt tip, erect, and densely covered with white, pink, or reddish flowers, only a few of which are open at any time. The peduncle of the flower spike is usually covered with short glandular hairs. Individual flowers are ~1/8" long, and have five tepals (white, light pink, or rose pink), 6-8 stamens with yellow, white, or pink anthers and two styles. Pennsylvania smartweed is a particularly variable species and may be difficult to identify unequivocally. If the stems zig-zag between nodes, if the flower stalks' peduncules are covered with glandular hairs, or if the flower spikes are short, cylindrical and erect, the specimen is likely to be Pennsylvania smartweed, but any or all of these features may be missing.

Persicaria

Persicaria pensylvanica

Pennsylvania smartweed [Blooms: Jul-Sep]

Dotted smartweed (Persicaria punctata) is a very common smartweed in Illinois wetlands. The upper stems produce spike-like racemes 2-6" long with white to greenish-white flower buds and flowers sparsely distributed along their length. Individual flowers are about 1/8" long with five white tepals covered with glandular depressions (best viewed with a hand lens). There are 6-8 stamens with red or pink stamens; the single style divides into two or three branches near its base. The flowers only open at their tips. The single seed is three-angled, oblong, and shiny brown to black; it remains tightly enclosed in the tepals as it develops. In Jackson Park, only dotted smartweed and waterpepper (Persicaria hydropiper) have glandular depressions on the surface of the flower tepals.

Persicaria

Persicaria punctata

dotted smartweed [Blooms: Aug-Sep]

A relative of the smartweeds and lady's thumb, jumpseed consist of a single, unbranched stem 1-2' tall with an apical inflorescence that can add an additional 16". Flowers are brilliant white, tiny (<3/16" across), with 4 sharply pointed petals (actually, sepals); 4-5 white stamens and a style are visible if you have really good eyesight. Flowers are widely spaced along the flower stalk on very short green stalks. Jumpseed is easy to tell from other smartweeds by the very long inflorescence with sparsely distributed flowers and very large leaves.

Persicaria

Persicaria virginiana

jumpseed [Blooms: Jul-Aug]

Reed canary-grass is a very widespread species (the native range is circumboreal in the Northern Hemisphere) that is listed as "vulnerable" in Illinois. It is a wetland grass that reaches heights of 3-5 feet; plants tend to be widely spaced on Jackson Park although they are known to produce clonal colonies elsewhere. The leaves are flat, alternate, and evenly spaced along the culm. The leaf blades reach up to 12 long and 3/4" across; they are green or blue-gray and hairless with continuous (but rough-textured) margins. The leaf base is much wider than the culm (stem) which it clasps tightly; the leaf sheaths look like an extension of the leaf in both color and appearance. When reproductive (early-midsummer), the culms produce a narrowly-pyramidal panicle up to 10" long and 2-3" across of spikelets that bear the florets. Spikelets are initially green but fade over time to a light tan color. The stem and leaves all turn a diagnostic light tan during the late fall and winter; the leaves mostly remain attached.

Phalaris

Phalaris arundinacea

reed canary-grass [Blooms: May-?]

Sweet mock-orange inflorescences are racemes with 5-7 fragrant flowers; the most basal pair of flowers arise directly from the leaf axils. Individual flowers are 1-1.5" across, have four triangular green sepals, four brilliant white petals, 20-50 white stamens with orange anthers, and four white styles with yellow-orange stigmas. The styles are closely appressed proximally, separate distally.

Philadelphus

Philadelphus coronarius

sweet mock-orange [Blooms: May-Jun]

Cleft phlox flowers are supported by 1" pedicels, are 3/4" across, white or pale violet, with a tubular corolla that flares into five petal-like lobes that are each deeply cleft at their tips; the throat is very narrow. A three-lobed stigma and the orange anthers of the stamens lie just within the opening to the throat of the flower. Cleft phlox is endemic to the Midwest. The cleft petal lobes distinguish cleft phlox from all other Phlox species.

Phlox

Phlox bifida

cleft phlox [Blooms: Apr-?]

Woodland phlox is a 1-1.5' tall plant with a fuzzy to hairy stem, light green or reddish brown in color. Leaves are opposite (or sometimes in a three-leaf whorl), sessile or clasping the stem, three times longer than wide, lance-shaped with smooth margins, and fuzzy to hairy overall with short hairs around the margins. The flowers are 1" across, pale blue-violet, lavender, or (rarely) white, and with a long, narrow tubular throat that abruptly flares into five petal-like, spoon-shaped lobes. The calyx is green or reddish-green, hairy, with five long, narrow teeth almost half the length of the flower, spreading near their tips. The five stamens and style are hidden within the throat. Woodland phlox has relatively broader leaves than other Phlox species and has a more intense blue-violet (and less pink) color.

Phlox

Phlox divaricata

woodland phlox [Blooms: Apr-May]

Smooth phlox is a 1-2' tall plant with an unbranched, hairless stem topped with a slightly domed cluster of 3-20 pink or lavender flowers. Each flower is about 3/4" across and has a long, tubular throat that abruptly flares into five petal-like lobes; each lobe is wedge-shaped and overlaps the next lobe clockwise. The calyx (also hairless) consists of five triangular segments that taper rapidly to sharp points; the calyx is <1/3 the length of the corolla tube. The five stamens and single style with a three-part stigma either lie within the corolla tube or are just visible in the throat. After fertilization, a narrow seed capsule filled with numerous seeds fills the persistant calyx. Smooth phlox prefers moist to wet habitats. Smooth phlox flowers resemble prairie phlox (P. bifida) but the latter species is quite hairy on the stems, leaves, and the exterior of the flower (the calyx); smooth phlox is hairless. Checking the hairiness (or lack thereof) of the calyx is the quickest way to tell prairie phlox from smooth phlox.

Phlox

Phlox glaberrima interior

smooth phlox [Blooms: Jun-Aug]

Prairie phlox is a compact, single-stemmed, plant 1/2-1.75' tall with (typically) a dome-shaped cluster of flowers at the apex. Individual flowers are 1/2-3/4" across, pink or lavender (rarely white); the corolla is tubular with five wedge-shaped, petal-like lobes often with darker markings (nectar guides) near the throat; the corolla is hairy on all external surfaces. The throat is very narrow; the five stamens with yellow anthers are recessed but just visible. The very short, tubular, hairy calyx base is green, with five long, narrow teeth that extend parallel to the narrow throat (also hairy) of the corolla. The fruit is oval and shorter than the calyx (in which it develops); when ripe, the capsule splits explosively, flinging the seeds in all directions. The species name ("pilosa") means "hairy" in Latin, and this species is indeed hairy on almost every surface. Prairie phlox flowers resemble smooth phlox (P. glaberrima) and, to a lesser extent, woodland phlox (P. divaricata), but the former species is quite hairy on the stems, leaves, and the exterior of the flower (the calyx); smooth phlox is hairless. Checking the hairiness (or lack thereof) of the calyx is the quickest way to tell prairie phlox from smooth phlox; checking the hairiness of the exterior of the corolla tube will distinguish woodland phlox (hairless) from prairie phlox (hairy).

Phlox

Phlox pilosa

prairie phlox [Blooms: Apr-Jun]

Giant reed is a grass that grows 4-16' tall (the tallest native grass in Illinois), often in dense, clonal stands. The culm (stem) is greyish-blue or light green; the base of the culm may be 15 mm (about 5/8") across. The culm ends in a panicle up to 1.5' long and half as wide of spikelets. When the florets are blooming, the panicle of spikelets has a reddish, silky appearance. Each spikelet is 12-17 mm long containing 3-7 florets. At the base of the spikelet is a pair of scale-like glumes (bracts) at about a 30° angle to each other; the base of the upper glume is nested inside the base of the lower glume, and both have a long, tapered, pointed tip. The glumes are typically 4-6 mm (1/4") long. Above the glumes, along the central axis of the spikelet (rachilla) are a series of progressively-shorter bracts (lemma and palea — more delicate versions of glumes — surrounding each floret) and tufts of silky hairs 1 cm long attached to the rachilla and obscuring the florets. The most basal floret is either sterile or is staminate; the remaining florets containing both male and female reproductive organs (= "perfect"). Staminate and perfect florets contain 1-3 stamens with purple anthers; perfect florets also have two long, feathery styles. The florets are wind-pollinated. After fertilization, individual seed grains replace the florets.

Phragmites

Phragmites australis

giant reed [Blooms: ?early-midsummer]

Clammy groundcherry flowers arise at the junction of two branches or at a leaf axil on 1/4", arching pedicels that permit the flower to droop. The flowers are up to 3/4" across, consisting of a green calyx half the length of the flower with five triangular teeth, a funnel-shaped, pale-yellow corolla with five shallow lobes, five stamens with large, creamy-yellow anthers, and a single central pistil. In the interior of the corolla surrounding the ovary are five brown smudges, one on each corolla lobe, that merge centrally into a purple-brown ring covering the ovary. Both the pedicel and the calyx are also covered with fine white hairs. After fertilization, the flowers are replaced by green (later brown) hollow husks (a persistant calyx), heart-shaped in longitudinal section, covering a 1/2" diameter spherical, green fruit that becomes yellow when ripe. All parts of clammy ground cherry contain a glycoalkaloid poison called solanine that causes a series of unpleasant and sometimes potentially fatal symptoms; clammy groundcherry is avoided by mammalian herbivores. Only the RIPE fruit is edible.

Physalis

Physalis heterophylla

clammy groundcherry [Blooms: Jul-Aug]

Smooth groundcherry flowers are yellow, bell-shaped, with five purplish-brown patches near the center, five stamens with yellow or purple anthers, and a single pistil; the flowers are suspended from a purplish-green pedicel 3/4-1" long. After fertilization, the flowers are replaced by a tomatillo-like fruit (often with ten purple meridional lines) that is a green (later brown) hollow husk (a persistant calyx) that is heart-shaped in longitudinal section, covering a 1/2" diameter spherical, green miniature tomato that becomes yellow when ripe. All parts of smooth groundcherry contain a glycoalkaloid poison called solanine that causes a series of unpleasant and sometimes potentially fatal symptoms; smooth groundcherry is avoided by mammalian herbivores. Only the RIPE fruit is edible (said to taste like an underripe strawberry).

Physalis

Physalis longifolia

smooth groundcherry [Blooms: Jun-Aug]

Ninebark produces round or domed clusters (racemes) of 30-50 flowers on the tips of young stems. Individual flowers are about 1/2" across; they have a light green calyx with five triangular teeth, five white petals, 30-40 pink-tipped stamens, and 3-5 styles with yellow stigmas. The inside surface of the flower between the styles and the base of the stamens (the hypanthium) is prominently colored tan, orange, or red. After fertilization, each flower produces 2-5 adjacent fruits "follicles"), greenish-red in color, drooping from the long, slender flower pedicels. Single follicles contain a single, hard seed; the follicles are about 8 mm long with a slender, pointed beak protruding from one side. There are two varieties of ninebark characterized by whether the surface of the follicle is hairy; the variety present in Jackson Park (var. intermedius) has a hairy surface.

Physocarpus

Physocarpus opulifolius

ninebark [Blooms: May-Jun]

Obedient plant flower spikes are up to 10" long, and have four rows of horizontal, tubular flowers or flower buds, with a stem densely covered with fine hairs (usually invisible beneath the tightly packed flowers). Individual flowers are purplish-pink, lavender, or white, with darker spots or stripes on the interior. Each 1" long flower consists of a hood-like upper lip and a broad lower lip with two small lateral lobes and a larger medial lobe. Four stamens with purple anthers lie just below (but within) the upper lip. The style lies among the stamens but is slightly longer; it bears a bifurcated stigma. The ~1/2" long calyx is green, tubular, with five sharp, flaring triangular lobes; it is densely covered with short, fine hairs. The fruit consists of four nutlets housed in the persistant calyx. Obedient plant will grow in most sunny habitats but prefers moist sites near water.

Physostegia

Physostegia virginiana

obedient plant [Blooms: Jul-Oct]

Pokeweed inflorescences are cylindrical, 3-6" long and 1" in diameter with 1/4" flowers radiating in all directions on short green or white pedicels. Individual flowers have five pink or white sepals and ten white stamens in a circle around fused carpels that form a lobed dome with ten tiny, thread-like styles in the center; petals are absent. The fruit is a 1/4" wide M&M-shaped berry that becomes dark purple and shiny when ripe; the pedicels also turn reddish-purple. Pokeweed is impossible to confuse with any other local plant. Children appear to be especially sensitive and may need hospitalization after eating only a few ripe berries.

Phytolacca

Phytolacca americana

pokeweed [Blooms: Jun-Oct]

English plantain is a Eurasian exotic that is a familiar lawn weed, one with a wirelike, leafless, five-angled flower stalk 6-18" tall. At the tip of the flower stalk is a 1/2-3" long cylindrical flower spike, initially grey-green but turning brownish as the flowers open. Individual flowers have four sepals, and four petals, but their most obvious character is the long filamentous stamens with white anthers which protrude in all directions from the flower spike. The styles are white, filamentous, and fuzzy. The flowers usually open sequentially from the bottom to the top of the flower spike, first as functional females with protruding styles, then as functional males with prominent stamens; the flower spikes thus typically consist of (from top to bottom): (1) unopened buds, (2) flowers with functional styles, (3) flowers with functional stamens, (4) developing seed pods. The flowers are wind-pollinated.

Plantago

Plantago lanceolata

English plantain [Blooms: May-Aug]

Common plantain is an introduced plant commonly found in lawns and disturbed areas. The flower stalks are erect, 4-20" long; the lower third is green and unadorned while the upper two-thirds is densely covered with 1/8" green flowers. Individual flowers consist of four green sepals with a green keel and membranous margins above a single green bract, four filamentous stamens with tan to purplish anthers, a single white style, and a four small, papery, petals. The flowers are wind-pollinated. The fruits are rounded, egg-shaped capsules about 1/8" long. Common plantain is nearly indistinguishable from (the native) black-seeded plantain (Plantago rugelii); the two species differ only in the details of the sepals and seed pods. (Common plantain's seed capsule is egg-shaped and splits around the middle; black-seeded plantain's seed capsule are 2-3 times longer than wide splits nearer the bottom.) One, more ephemeral, character may help distinguish the two species in the field. According to Minnesota Wildflowers, the base of the leaf stalks of the native species (Rugel's plantain, P. rugelii) are dark red or purple in color; the base of the leaf stalks of the exotic common plantain (P. major) are uniformly green. Rugel's plantain is probably as common and tolerant of a range of habitats as common plantain, but specimens of this plant tend to be reflexively referred to "common plantain."

Plantago

Plantago major

common plantain [?-Aug]

Mayapple produces a single, hairless stem that branches no more than once; each stem thus has either a single leaf (infertile stems) or two leaves (fertile stems). Fertile stems produce a solitary nodding flower, 2-3" across, that is hidden beneath the leaves where the two leaves branch on the stem. The flowers contain 6-9 brilliant white petals and a ring of 12-18 tan stamens with large, banana-shaped anthers, all surrounding a surprisingly large, yellow ovary topped with a button of a stigmata. The fruit is a large (1.5" long), ellipsoidal berry, yellow when ripe. All parts of the plant are poisonous including the green fruit, but the ripe (yellow) fruit is edible (in small quantities).

Podophyllum

Podophyllum peltatum

mayapple [Blooms: Apr-May]

The stems and flower stalks of Jacob's ladder are green to reddish-green and hairy; the flowers occur in panicles of floppy flowers on 1" long pedicels. The flowers are bell-shaped and baby-blue in color, 3/8" across with fine longitudinal veins. There are five stamens with white anthers and a long style tipped with a Y-shaped stigma. The stamens do not project beyond the flower margins, but the style does. The fruit is an ovoid, three-celled, seed capsule about 1/4" long held in the remnants of the calyx. Jacob's ladder prefers shady woodlands. This species is similar to Greek valerian (Polemonium vanbruntiae) but the latter species has stamens that extend beyond the flower margins (and does not occur in Illinois).

Polemonium

Polemonium reptans

Jacob's ladder [Blooms: Apr-May]

Solomon's seal is a 2-3.5' tall plant with a single, unbranched, hairless, arching stem. On the underside of the stem are 12-20 dangling clusters of flowers (2-3 flowers/cluster). The flowers are 1/2-1" long, whitish- or yellowish-green, tubular, with six lobes/tepals fused for most of their length but that flare slightly at their tips; the interior of the flower contains six stamens with yellow anthers and a single style. The fruit is a 1/4" diameter spherical berry, initially green, dark blue-violet or -black when mature. When in bloom or bearing fruit, Solomon's seal is distinctive and easy to identify; when not in bloom, the leaves of Solomon's seal can be difficult to distinguish from those of false Solomon's seal (Maianthemum racemosum) and starry false Solomon's seal (Maianthemum stellatum). (Both Maianthemum sp. have short petioles on their leaves and their flowers are terminal, at the end of the stem, rather than hanging down from the stem.) Polygonatum biflorum is sometimes (incorrectly) referred to as Polygonatum commutatum. The "Solomon's seal" in the name refers to scars on the rhizome fancied to look like a Hebrew seal. I have to admit I just don't see it.

Polygonatum

Polygonatum biflorum

Soloman's seal [Blooms: May-Jul]

Prostrate knotweed is a summer-blooming Eurasian exotic that is widespread and ubiquitous across Illinois. One to five 2-3 mm long flowers occur in a cluster at the base of the leaves; the flowers have very short petioles but may appear sessile. Individual flowers have five white or green and white sepals, no petals, five or eight stamens with yellow anthers, and three styles (one for each carpel) fused into a single pistil with a tripartite yellow stigma fringed with short hairs. The fruit develops within the persistant sepals of the flower. Prostrate knotweed is not fussy about its habitat and withstands a fair amount of foot traffic.

Polygonum

Polygonum aviculare

prostrate knotweed [Blooms: Jun-Sep]

Pickerel weed is an aquatic plant with emergent leaves and flower spikes; it is native to the New World. Each flower stalk is up to 3' tall (usually shorter) and bears a single leaf whose petiole is wrapped by a thin sheath. The flower stalks bear a flower spike ~5" long, densely covered with blue-violet flowers and unopened flower buds; below the spike, the flower stalk is wrapped in a sheath. Individual flowers are ~1/2 across; the corolla has three upper lobes (with 1-2 yellow spots on the middle lobe) and an additional three lower lobes; the exterior of the buds and the flowers is covered with long, white hairs. There are six stamens, usually three emergent and three recessed deep in the flower. Like purple loosestrife (Lythrum salicaria), pickerel weed has tristylous flowers with each plant producing flowers with one of three distinct lengths of the styles (and thus the position of the stigma) and three complementary lengths of the stamens (call them long, medium, and short). If the styles are L, the stamens are M and S; if the styles are M, the stamens are L and S, and if the styles are S, the stamens are L and M. Presumably, these complications enhance genetic outcrossing. For more information, see Price and Barrett (1984) Biol. J. Linn. Soc. 21: 315-329 and Gettys and Wofford (2008) J. Heredity 99: 558-563.

Pontederia

Pontederia cordata

pickerel weed [Blooms: Jun-Sep]

Eastern cottonwood is dioecious; flowers are either male or female and occur on separate trees. The flowers, whether staminate or pistillate, are produced on catkins 2-3" long; the flowers are wind pollinated. Male catkins are produced in clusters of 2-4 near branch tips; they are bright red or yellow, cylindrical, and densely covered with male florets. The male florets have a fringed bract at their base, above which is a basal disc with 30-40 reddish or yellowish stamens. Female catkins are solitary (not in groups), cylindrical, and green, covered with numerous female florets on slender petioles. Each female floret rests on a fringed bract above which is a dish-shaped three- or four-carpelled basal disc with a single, oval pistil about 8 mm long with 2-4 apical, yellowish, flattened stigmas with undulate margins. After fertilization, the female catkins elongate to a length of 4-6" while individual ovaries enlarge; at maturity, each fruit splits to release 30-50, 2 mm long, seeds suspended on cottony hairs. The seeds are both wind and water dispersed.

Populus

Populus deltoides

Eastern cottonwood [Blooms: Apr-May]

Common purslane has no inflorescence per se; flowers occur alone or in small terminal clusters. Individual flowers are 1/8-1/4" across with two or four green sepals, 4-6 yellow petals with notched tips, 6-12 stamens with yellow anthers, and a five-lobed style with 3-6 stigmas. Fertilized flowers are replaced by an oval or urn-shaped capsule about 8 mm long that splits open along a meridional seam to release the tiny, dark brown or black seeds.

Portulaca

Portulaca oleracea

common purslane [Blooms: Jun-Sep]

In late spring and early summer, curly pondweed produces both flowers and turions (a detachable, dormant bud, a.k.a. a "winter bud"). Cylindrical flower spikes 1-1.5" long arise from the tips of the stems or the axils of upper leaves; peduncles up to 3" long hold the flower spikes just above the water. Each flower spike may have 3-5 whorls of flowers. Individual flowers are tiny (3 mm across); they consist of four greenish-brown or greenish-red sepals, four stamens with a ladle-shaped appendage, and four ovules topped by a four-part style. Flowers may be pollinated by either wind or water. Fertilized ovules produce a dry seed (a maximum of four per flower) that is generally oval but asymmetrical in detail with a knobby keel along one edge and a long, curved beak or tooth at the opposite end. Seed germination has never been observed. Simultaneously, the plant produces turions — rosettes of small, holly-like leaves that overall have a cone-like appearance — from the tips of stems and leaf axils. After the fruits and the turions are released, the rest of the plant degenerates over the course of the summer. The turions sink to the bottom of the water body and root, forming small plants that overwinter.

Potamogeton

Potamogeton crispus

curly pondweed [Blooms: May-?]

Silverweed is a low, sprawling native plant that occurs everywhere in North America from the southwest through northern Canada. The prominent red stolons give rise to both new rooted nodes where the stolons encounter wet soil and may also give rise to new leaves. There is a basal rosette of large (12" long x 4" wide) odd-pinnate leaves with 5-11 opposite leaflet pairs and a single terminal leaflet. Flower pedicels 2-6" long arise from stolon nodes. The flowers are bright yellow, solitary, and 3/4" across. Each flower has five light green, hairy sepals; 5-15 oval, yellow petals; a ring of ~20 yellow stamens with large flat anthers; and a central disc of 20 to over 100 yellow pistils. The sepals are shorter than the petals. Silverweed prefers sandy habitats like beaches.

Potentilla

Potentilla anserina

silverweed [Blooms: Jun-Aug]

Rough cinquefoil is considered to be native to both North America and Eurasia. Flowers may develop from the axils of the upper leaves but more usually occur (as a panicle of cymes) in a terminal inflorescence on flower stalks 1-2' tall. The flowers are small (1/3-1/2") and pale yellow; the petals are distinctly heart-shaped with narrow bases and the sepals are triangular and slightly longer than petals. About 15-20 yellow stamens surround a dome-shaped, yellow receptacle covered with styles. Beneath the sepals are five green oval bracts about the same length as the sepals when the flower is in bloom. Fruits develop as dry seeds (achenes) in the persistent flower calyx. Note that rough cinquefoil’s leaves have three leaflets, common cinquefoil's leaves have five, and prairie cinquefoil's leaves have 7-11.

Potentilla

Potentilla norvegica

rough cinquefoil [Blooms: Jun-Sep]

Sulfur cinquefoil flowers are 3/4" across, pale yellow with a golden center. Beneath the flowers are green bracts about the same length as the sepals but narrower. The sepals are equilateral triangles that are shorter than the petals while the petals are heart-shaped with the narrow point at the base of the petal (where the yellow color is often more intense). There are 25-30 stamens surrounding the central receptacle; the anthers have one or more central dark spots contrasting strongly with the generally yellow anther (but these spots may be difficult to see). Sulfur cinquefoil is similar to prairie cinquefoil, but sulfur cinquefoil's flowers are yellow, not cream colored and its leaves are palmately compound, not pinnate. After fertilization, the sepals close over the ovary forming a capsule around the maturing seeds. The seeds are dry achenes less than 2 mm long with a coarsely wrinkled, brown surface. Sulfur cinquefoil was accidentally introduced to North America from Europe; the first recorded observation was in Montreal in 1852. By 1879, sulfur cinquefoil had become naturalized in New York state; by 1900, it was spreading across New England and the upper midwest. (So sulfur cinquefoil probably wasn't around for the Columbian Exposition in Jackson Park in 1893.) It spreads aggressively in disturbed areas.

Potentilla

Potentilla recta

sulfur cinquefoil [Blooms: May-Jul]

Common cinquefoil is a sprawling plant less than a foot tall that produces numerous prostrate stolons up to 3' long. Both the stems and the stolons are initially green but become more reddish. The leaves are alternate and palmately compound with five leaflets, each with serrated margins; the leaflets are three to four times longer than wide. The sparse flowers develop singly on long pedicels that arise from the axil of some compound leaves. They are bright yellow and 1/2" across with triangular sepals shorter than petals; the petals are narrowest at their base and usually rounded at their distal edge. About 20 stamens with yellow anthers (turning reddish with age) surrounded a central mass of styles. Common cinquefoil has flowers and leaves that are superficially similar to those of mock strawberry (Duchesnea indica). However, the leaves of common cinquefoil have extremely sharp-edged, well-defined teeth on the leaf margins (strongly resembling the edge of a hand saw), not the bluntly-tipped teeth of mock strawberry. The five small bracts (leaves) just below the sepals in mock strawberry, each with three pointed lobes at its tip, are present in both the flowers and berries are diagnostic of mock strawberry; they are absent in common cinquefoil. Note that rough cinquefoil’s leaves have three leaflets, common cinquefoil's leaves have five, and prairie cinquefoil's leaves have 7-11 leaflets.

Potentilla

Potentilla simplex

common cinquefoil [Blooms: May-Jul]

Shooting star's smooth, leafless flower stalk is reddish-green, bearing 6-20 (sometimes up to 40) nodding flowers at its apex that are suspended from delicate pedicels. Each flower has a green calyx with five short, triangular green lobes, five white or pale lavender petals reflexed backwards (upwards) and often twisted along their lengths. A "reproductive cone" (five yellow to purple stamens tightly appressed around a single, purplish-green central style) extends down from the yellow petal bases. The fruit is a short, ovoid seed pod, initially green, turning reddish-brown with maturity, 1/4-3/4" long with a pointed tip that is oriented vertically (the curvature of the pedicel reverses after fertilization); it is filled with small, dark seeds. The flowers of shooting star are superficially similar to those of horse nettle (Solanum carolinense) but the latter do not hang from a long stalk like shooting star (and have lots of prickles and spines that shooting star lacks). The convergent evolution of "reproductive cones" in both shooting star and horse nettle is an adaption to increase the efficiency of buzz pollination by large bees, especially bumblebees. The older name for this species ("Dodecatheon meadia") is no longer considered valid.

Primula

Primula meadia

shooting star [Blooms: Apr-May]

Heal-all (a.k.a., self-heal) is a native species superficially similar to ground ivy (Glechoma hederacea) or early-season henbit (Lamium amplexicaule). Heal-all has the characteristics of other low-growing plants in the mint family — an upright, four-angled stem, with lines of hairs along the ridges, 1' tall or less, with a short (1-2") spike of flowers at the apex — and is thus easy to overlook. But the tiny (1/2" long), tubular, two lipped flowers are distinctive (and charming). The light purple or blue upper lip is bent at right angles to form a hood over the aperture with the four stamens and single style with a bifurcated stigma at its tip curving along inside of the hood. The lower lip is divided into three lobes, the middle one white and fringed; the two smaller lateral lobes are the same color as the hood. The hood of the upper lip also sports a "mohawk" haircut of relatively long hairs along the crest of the hood. The flower calyx is light green or reddish, hairy along the edges. After fertilization, four tiny, brown, finely-ridged nutlets develop within the persistant calyx; the seeds are reported to be dispersed by a mechanism that uses the energy in raindrops impacting the calyx to fling the seeds away from the mother plant. The leaves are opposite, up to 2" long and half as wide with a short petiole; they are egg- or lance-shaped with a central vein that is hairy on the underside. Heal-all prefers moist habitats with a history of disturbance.

Prunella

Prunella vulgaris

heal-all [Blooms: Jun-Aug]

American plum flowers first appear before or at leaf emergence; they occur in roughly spherical clusters (umbels) of two to five flowers, arising from leaf axils. Each flower is ~1" across, held away from the twig at the base of the umbel on 1/2-1" petioles; there are five egg-shaped petals with narrow bases, white with a touch of pink, five narrow, somewhat fleshy, green sepals much shorter than the petals, a single style, and numerous (10-30) stamens with tan anthers. The fruits are about 1" across, initially green but turning reddish-purple with the waxy bloom typical of plums when ripe; inside is a single seed (a "stone," like a peach). Because this tree usually flowers when the leaves are only beginning to open, it produces an especially showy display. It is widespread across Jackson Park.

Prunus

Prunus americana

American plum [Blooms: Apr-May]

The floral inflorescence in sweet cherry is a flat-topped corymb of two to six cup-shaped flowers that appears in early spring as the new leaves unfold. Each flower is 1-1.5" in diameter with five green sepals reflexed back along the petiole; five pure white petals; a ring of 20-30 stamens each with a white filament tipped with a yellow, ball-like stamen; and a single pistil with a terminal knob-like, greenish stigma. The fruit is a red to dark purple drupe (stone fruit) 1/2-1" in diameter (a typical cherry).

Prunus

Prunus avium

sweet cherry [Blooms: Apr]

European bird cherry It has showy white flowers (so is widely planted as an ornamental) and reaches heights of 30-40'. Blooms are produced in elongate, cylindrical racemes of 15-50 flowers at the tips of twigs, similar to but shorter than those of chokecherry (Prunus virginia). Individual flowers consist of five green, broadly-spreading or reflexed sepals (longer than wide); five white or cream colored petals that are 1/4-3/8" long, oval but widest in the center; 10-30 stamens half the length of the petals around a cup-shaped, often green hypanthium (hairless externally); and a single central pistil. The fruit is a small, black drupe (cherry) with an extremely bitter taste to mammals, but it is much loved by birds, who disperse the pits. European bird cherry is very similar to another species present in Jackson Park, chokecherry. European bird cherry tends to be more tree-like in habit than chokecherry and tends to have shorter stamens (half the length of the petals) than chokecherry (as long as the petals). It's not clear how much of this expansion is due to Park District policy and how much is due to natural seed dispersal.

Prunus

Prunus padus

European bird cherry [Blooms: Apr-May]

Peach flowers arise along young branches, blooming beginning before the leaves have opened in the spring; the flowers are usually solitary but occasionally occur in pairs. Individual flowers are 1-1.5" long consisting of a burgundy-colored calyx with five rounded apical lobes (sepals); five spreading pink (rarely, white) petals, oval with abruptly narrowed bases ("clawed"); 15-30 stamens with pink filaments and yellow to orange anthers; and a pistil with a single light green style nearly as long as the stamens. Fertilized flowers are replaced by green, fuzzy ovoids, eventually up to 3" long and across and containing a single seed; peach-colored when mature.

Prunus

Prunus persica

peach [Blooms: Apr-May]

Sand cherry is a 4-8' tall shrub; the Great Lakes variant of this species (Prunus pumila spp. pumila) is restricted to the states (and the Canadian province) that touch on the Great Lakes. Blooms occur in umbels of 1-3 flowers; flowers open before the leaves but may persist after some leaves have emerged. Individual flowers are about 1/2" across, consisting of five sepals with rounded tips that are about a third the length of the petals; five white, round- or egg-shaped petals; 10-30 white stamens with yellow anthers emerging from a reddish, cup-shaped hypanthium; and a single, central style. The fruit is a reddish-purple to black, shiny cherry (drupe) about 1/2" in diameter. Sand cherry is found along the shores of the Great Lakes on beaches (sandy, gravelly, or rocky), dunes, and the swales between dunes.

Prunus

Prunus pumila

sand cherry [Blooms: Apr-May]

Black cherry (Prunus serotina) is a is a deciduous tree that can grow up to 80' tall. It typically has a single central trunk below and leafy crown that is taller than wide. Flowers occur in racemes 4-6" long with 20-60 1/2" wide flowers packed around the elongated inflorescence. Individual flowers consist of five green, triangular sepals, five white petals broader at their distal tips and at least three times longer than the sepals, 10-30 stamens with yellow anthers around a reddish-orange hypanthium, and a single, central pistil with a flattened stigma. After fertilization, each flower produces a globoid, fleshy drupe about 1/4" across. The immature cherries are green; as they mature the fruit turns first dark red, they purple-black at maturity. These fruits are sweet but slightly bitter; the black cherry you buy in the grocery store is larger (at least 1/2" across), sweeter, and a species native to Eurasia (Prunus avium).

Prunus

Prunus serotina

black cherry [Blooms: May-June]

Japanese flowering cherry is an exotic from East Asia widely grown in North America as an ornamental (for its showy spring flowers). The flowers occur is small clusters of 2-5 white, pale pink, or deeper pink flowers that (unlike most cherries) dangle face-down beneath the stems from short spurs. The fruit consists of small, round drupes that turn black when mature. Leaves, stems, and fruit, and seeds are toxic to mammals. Many of the cultivars of Japanese flowering cherry are highly hybridized and nearly unrecognizable as being derived from Prunus serrulata.

Prunus

Prunus serrulata

Japanese cherry [Blooms: Apr-May]

Chokecherry is a shrub or small tree 8-25' tall. Flowers occur in spectacular racemes ~6" long with 15-20 white, 1/2" wide, bowl-shaped flowers with an orange-yellow center (hypanthium); the flowers are attached to a central, greenish-yellow stalk. Individual flowers consist of five sepals (initially green, later turning yellow) shorter than the petals, five white petals that narrow sharply near their bases, 15-20 stamens about as long as the petals, and a pistil with a single style. Crushed leaves smell strongly of bitter almonds. Fruit is a red to black globular drupe <1/2" wide that contains a single hard-coated seed (stone) and has a VERY bitter taste; the seed contains high levels of hydrogen cyanide. The fruit is eaten by a wide variety of mammals and birds; the flesh of the fruit traditionally was one of the components of pemmican in indigenous cultures. (The hydrogen cyanide is not a danger unless the hard shell of the seed is broken open.) Chokecherry is similar to wild black cherry (Prunus serotina), but P. serotina has incurved teeth on its leaf margins. Chokecherry is very similar to an exotic also present in Jackson Park, European bird cherry (Prunus padus). European bird cherry tends to be more tree-like in habit than chokecherry and tends to have shorter stamens (half the length of the petals) than chokecherry (as long as the petals). Chokecherry in Jackson Park is often infested with black knot fungus (Dibotryon morbosum).

Prunus

Prunus virginiana

chokecherry [Blooms: Apr-May]

Hoptree (a.k.a., wafer ash) is a large shrub with a rounded, irregular crown and (usually) a robust central trunk up to 6" across. Hoptree may produce single-sex (male or female) or bisexual (male and female organs both present) flowers on the same tree. Individual flowers are about 1/4" across, regardless of gender. Perfect (bisexual) flowers have 4-5 greenish sepals, 4-5 narrow, creamy white petals, 4-5 stamens with hairy white bases and yellow anthers, and a single, flattened green pistil. Male flowers are more or less identical but lack the pistil; female flowers are more or less identical but lack the stamens. The fruits are single seeds 1-1.5" long with a broad, flattened, papery wing extending almost all the way around the seed.

Ptelea

Ptelea trifoliata

hoptree [Blooms: May-Jun]

triped squill is another early spring wildflower native to western Asia and the Caucasus; it tends to grow in clumps of plants 4-6" across. There are (only) two dark green, basal, hairless leaves up to 6" long and ~1/2" wide that widen towards their tips; the margins are smooth. A cluster (raceme) of 3-6 flowers are present on a stalk ("scape") 4-8" tall; overall, the cluster and scape resemble the related wild hyacinths. Each flower has six white tepals with a medial blue stripe. The filaments of the six stamens are flattened and fused together to form a white central, lobed, hollow cone that surrounds the style; the anthers are yellow and lie just inside the tip of the cone. This plant is one of the earliest to bloom in the spring in Jackson Park, but goes dormant in the late spring, basically biding its time until the next year. It prefers moist, well-drained soils.

Puschkinia

Puschkinia scilloides

striped squill [Blooms: Mar-Apr]

Slender mountain-mint flowers occur in small terminal clusters at the tips of the upper stems with distinctive very long, narrow bracts with spine-like tips just beneath the clusters; the bracts are densely covered with short, curled hairs on the blade and longer, bristly hairs along the margins. Individual flowers are tubular, white with scattered purple dots, and about 1/4" long; there is a calyx that is divided several slender green lobes. The corolla is divided into two parts, an upper lip and a lower lip that is divided into three lobes. The four stamens and two styles are also white, but the anthers are purple. The styles have a bifurcated stigma. Slender mountain mint is very similar to Virginia mountain mint (Pycnanthemum virginianum), but several characters make it straightforward to distinguish them. Leaves on slender mountain mints are always less than 1/4" wide and the stems are hairless; Virginia mountain mint will have the larger leaves more than 1/4" wide and has lines of white hairs on the stems. Slender mountain blooms earlier than Virginian mountain mint, but the blooming period of the two species overlaps. All parts of slender mountain mint give off a strong mint-like odor when crushed, but please restrain yourself from excessive foliage-crushing — it's not polite.

Pycnanthemum

Pycnanthemum tenuifolium

slender mountain-mint [Blooms: Jun-Aug]

Virginia mountain-mint flower heads are 3/4-1" across with up to 50 flowers; only a few flowers open at any one time. The flowers are hairy on the outer surfaces, white to light purple in color. Individual flowers are 1/4" across, tubular, and two-lipped; the lower lip is three-lobed with purple spots; four stamens with purple anthers emerge from the lower tube. There are two styles with deeply-notched tips that extend well beyond the edges of the lips of the corolla. The calyx that cups the flower is hairy, light green and has five triangular teeth.

Pycnanthemum

Pycnanthemum virginianum

Virginia mountain-mint [Blooms: Jul-Aug]

Male and female flowers of pin oakare spatially separated but often occur on the same branch. Female flowers have been reduced to only a short, green spike bearing three bright red styles; the female flowers emerge from leaf axils and may occur in clusters of up to three. The male flowers are borne on 1.5-4" long green catkins that dangle from bud clusters at the tip of the previous year's growth. The fruits are egg-shaped or elliptical (hence the species name) acorns 1/2-2/3" long with a deep reddish cap that covers about half the acorn.

Quercus

Quercus ellipsoidalis

Northern pin oak [Blooms: Apr–May]

In bur oaks, both male and female flowers are produced on the same tree, but they are widely separated; the flowers are wind pollinated. Male flowers are borne on drooping, yellowish-green catkins 2-5" long that hang from the tips of the previous year's twigs; individual male flowers consist of 5-20 stamens surrounded by a lobed calyx. Some sources (e.g., http://www.missouribotanicalgarden.org/plantfinder/PlantFinderDetails.aspx?taxonid=280704) assert that the female flowers of bur oak also occur on catkins, but this is incorrect. Instead, the female flowers occur alone or in groups of 2-3 that arise in the leaf axils of new leaves. Individual female flowers are about 3 mm (1/8") long; a short, reddish green stalk (a pistil) covered with appressed scales bears naked reddish-green or light green styles on its tip. The female flowers are wind pollinated. Both male and female flowers form after the leaves begin to unfurl; the male catkins precede the female flowers by one to several weeks. Fertilized female flowers produce one or two acorns; the acorns may be nearly sessile or hang from short (<1") stalks. Mature bur oak acorns are 1.5-2.5" long and the same across (including the caps) — they are the largest acorn of any oak. The caps (= cupules) cover at least half of the length of bur oak acorns, often so much that only a nubbin of the acorn is visible. The caps are covered with coarse scales that have an obvious keel and appear knobby; the marginal scales on the caps bear soft awns up to 8 mm (1/3") long that form a conspicuous fringe above the acorn — this is the "bur" that is referred to in the common name in analogy to the machine tool used for grinding. The acorns mature and germinate over a single summer; they do not need to be exposed to cold to germinate.

Quercus

Quercus macrocarpa

bur oak [Blooms: Apr–May]

Small-flowered buttercup is a native species that has flowers similar to several other buttercups but is distinguished by its broad range of leaf shapes — other buttercups don't have this wide a variety of leaf shapes on a single plant. The flowers are stalked in groups of one to three on the end of the stems. Each flower is 1/4" across with five lance-shaped or triangular petals that are shorter than the sepals. There are five broadly rounded sepals, a ring of 5-10+ stamens with yellow anthers, and a central mound of green carpels, each with a pistil. After fertilization, the carpels enlarge and the central mound elongates until it is ovoid; the fruits (achenes) are shiny and have small beaks.

Ranunculus

Ranunculus abortivus

small-flowered buttercup [Blooms: Apr-May]

Lesser celadine flowers arise singly from the axils of the upper leaves or on the ends of stems. Individual flowers are about 1" across with three light green sepals half the length of the petals, 7-12 yellow, oblong petals, and a ring of about 30 (yellow) stamens around a central group of about 15-20 (greenish) pistils. This species rarely produces fruit, instead reproducing asexually. The alternative name "Ficaria verna" is occasionally used for lesser celadine, but that name is now considered invalid.

Ranunculus

Ranunculus ficaria

lesser celadine [Blooms: Apr-May]

Hispid buttercup is a native species that gets up to about a foot tall; plants tend to become more sprawling as they grow. Flowers are 3/4-1" across, arising from the leaf axils on stalks with short, appressed hairs. Each flower has five light green sepals shorter than the petals and with long hairs on the outer surface, five shiny, yellow petals, and a ring of 5-10+ yellow stamens around a central mound of yellowish-green pistils. There is often a region at the base of the petals that is translucent and green-tinged. The sepals may lie directly under the petals or may be reflected so they lie parallel to the flower stem. After fertilization, the central mass of the flower enlarges and the other parts of the flower wither and fall away. Maturing fruits are green, shiny, laterally compressed, with a sharply angled margin and long, straight, tapering beaks pointing up at about a 60° angle; the seedhead looks distinctly spikey.

Ranunculus

Ranunculus hispidus

hispid buttercup [Blooms: May-Jul]

Pennsylvania buttercup is a native plant that is formally listed as "imperiled" in Illinois (which is at the southern limit of its range east of the Mississippi). The flowers arise from leaf axils on short stalks. Individual flowers are small (1/8-1/4" across) with five yellowish-green sepals, five shiny, yellow, egg-shaped petals, and a ring of 5-10+ yellow stamens around a central mound of green carpels and pistils. The sepals are longer than the petals, are reflexed back on the flower stem, and are covered with long hairs on the hidden surface. After fertilization, the carpels enlarge and the central mound elongates; individual mature fruits are laterally compressed with straight to sightly curved (but not hooked) beaks. Pennsylvania buttercup tends to prefer wetlands and similar environments.

Ranunculus

Ranunculus pensylvanicus

Pennsylvania buttercup [Blooms: Jul-?]

Individual flowers of hairy buttercup have five sepals, each 1/8-1/4" long with a sharp transverse fold at their base such that the sepals point down (are reflexed), parallel to the stem. There are five petals that are 7-10 mm long and 4-8 mm wide, roughly egg shaped, with the upper surface a brilliant, glossy yellow. Finally, two to three dozen yellow stamens with yellow anthers surround a yellowish-green central ovary with plate-like segments radiating out from the center of the ovary, each with a blunt, short style. The fruit develops by an enlargement of each of these segments, which remain attached to each other. Hairy buttercup is easily confused with early buttercup (Ranunculus fascicularis), but the sepals of early buttercup lie parallel to the petals (horizontal) while the sepals of hairy buttercup have a distinct transverse fold at their base such that the sepals lie parallel to the floral stem, at a steep angle to the petals.

Ranunculus

Ranunculus sardous

hairy buttercup [Blooms: May-Jun]

Cursed crowfoot flowers occur on the ends of the upper stems. Individual flowers are 6-8 mm across with five yellowish-green sepals about the same length as the petals, five (sometimes three or four) yellow, rounded petals, a ring of 5-10+ short stamens with yellow anthers, and a central hemispherical to gumdrop-shaped mass of green pistils. After fertilization, the central mass of pistils enlarges and elongates, producing a cylindrical mass of flat, smooth, kidney-shaped 1 mm long seeds with short, straight beaks.

Ranunculus

Ranunculus sceleratus

cursed crowfoot [Blooms: May-Jul]

Upright prairie coneflower (aka, "Mexican hat") is a 1-3' tall plant native to North America but an exotic in Illinois; it looks like English plantain (Plantago lanceolata) dressed up for a party. The stems are green and longitudinally ridged; they bear alternate, pinnatifid leaves with 5-11 elongate, narrow lobes. The upper stems produce flower stalks (peduncles) 2-12" long, minutely grooved, and lacking leaves; the peduncles are very "wire-like." The flowerheads are 1.5-3" long cylinders composed of numerous brown or purplish disk florets that bloom from the bottom of the cylinder to the top; at the base of the cylinder are 4-12 ray florets with drooping, 1/2-1.5" long, oblong petals with notched tips that are yellow, maroon, or yellow with basal maroon patches (the "party skirt"). This plant is unmistakable when in bloom. The imaged flower was photographed in Bobolink Meadow in July, 2010; I have not seen a specimen since.

Ratibida

Ratibida columnifera

upright prairie coneflower [Blooms: Jul]

Grey-headed coneflower's composite flowerheads sit individually on the tips of long, thin, ridged stalks; they have up to 15 drooping, 2" long, yellow ray florets and a central 3/4" tall gumball- or egg-shaped cone of 100-200 disc florets. The ray florets are sterile; the disc florets have both stamens (5) and styles (1). Beneath the flowerhead are two series of long, narrowly-triangular bracts. The disc florets mature progressively from the bottom of the cone to the top; immature disc florets are light green or grey, mature disc florets are brown, giving the portion of the cone they cover a fuzzy appearance. (Thus the analogy implicit in the common name to a grey, bald pate peeking through a head of brown, fuzzy hair.) After fertilization, the cone becomes a mass of small (2-4 mm long), brown seeds (achenes) that are devoid of a tuft of hairs.

Ratibida

Ratibida pinnata

grey-headed coneflower [Blooms: Jun-Oct]

In Japanese knotweed, axils of the upper leaves produce slender, fuzzy spikes 2-4" long, covered with white or greenish flowers; more than one spike can arise from an axil. The flowers arise in groups of 3-6 from papery sheaths on the spikes. Individual flowers are sessile, about 8 mm long, with a funnel-shaped calyx, five petal-like sepals with wings on their outer faces, no petals, 6-8 stamens, and a tripartite stigma on top of a bullet-shaped green ovary. The fruit is a single shiny, black, three-angled seed with three broad, whitish, wings. Japanese knotweed is a highly aggressive invasive, luckily uncommon in Jackson Park. I know of three places in Jackson Park where it grows (it is a perennial); the Park District has eradicated it in one of these locations.

Reynoutria

Reynoutria japonica

Japanese knotweed [Blooms: Aug-Sep]

In buckthorn, umbels of flowers arise from leaf axils. Flowers on a single plant may be perfect (both male and female organs present), but more commonly the flowers are dioecious with either all male (staminate) or all female (pistillate) flowers found on any given plant. Individual flowers are 1/4" across. They have four greenish-yellow, triangular, spreading sepals that together form a calyx and four petals that can't be easily seen without magnification; the "petals" in the flowers are actually sepals. Male flowers have four greenish stamens with cream-colored anthers; female flowers have a single style that has a tip divided into four branches. After fertilization, female (or perfect) flowers produce a shiny black, 1/4" wide, cherry-like fruit containing 3-4 seeds. Birds can eat the fruit without ill effects, but in humans the fruit produces stomach cramps and acts as a strong laxative (as indicated by the species name, "cathartica").

Rhamnus

Rhamnus cathartica

buckthorn [Blooms: May-Jun]

Jetbead flowers are solitary, arising on the tips of the green twigs. Flowers are elevated on 1/4-1/2" long stalks. There are four green sepals at the base of the flower, each with a bractlet half the length of the sepals that is located below the intersection of each pair of sepals. Four white, nearly circular petals alternate in position with the sepals. A greenish hypanthium covers the center of the flower with a four-lobed ridge marking its edges. Numerous (30-60) stamens with white filaments and yellow anthers, usually in four distinct clusters, lie inside the ridge; the stamens surround four pistils, each with a single style and a circular, terminal stigma. After fertilization, 1-4 fruits develop in the center of the flower that turn shiny black at maturity (the "jetbead"); the seeds remain attached to the persistant sepals until late in the fall and may persist through the winter.

Rhodotypos

Rhodotypos scandens

jetbead [Blooms: Apr-May]

Fragrant sumac is a native shrub that grows 2-8' tall. One-inch-long spikes of closely-packed flowers arise from leaf axils. Individual flowers are 1/8" long, tubular but less than twice as long as wide, with five greenish-yellow petals and a calyx of five short sepals fused at their bases; flowers are either perfect (with both male and female organs) or unisexual (either stamens only or pistils only). (If unisexual, all flowers on one plant are the same sex.) Male flowers have five stamens with yellow-orange anthers but no pistil; female flowers have a pistil with a Y-shaped tip but no stamens. After fertilization, the flowers are replaced by fruits 1/4-3/8" in diameter, roughly spherical, deep red, and exuberantly hairy; it contains a single stone (a seed with a hard coat). Fragrant sumac blooms before either smooth sumac or staghorn sumac and its fruit matures earlier.

Rhus

Rhus aromatica

fragrant sumac [Blooms: Apr-May]

Smooth sumac is dioecious — each plant produces only either male (staminate) or female (pistillate) flowers. Individual flowers are about 1/4" across with a green calyx with five teeth and a whitish green or yellowish green corolla with five spreading petals. The lobes and teeth range from lance-shaped to oval. Male flowers also have five stamens with large yellow anthers and style rudiments; female flowers have an ovary with three closely-packed, stout styles in the center and sometimes with rudiments of stamens. On female plants, after fertilization, the flowers are replaced with about 5 mm wide drupes containing a single straw-yellow stony seed. The fruits are initially green and densely covered with short hairs, turning an intense, deep red when mature.

Rhus

Rhus glabra

smooth sumac [Blooms: May-Jul]

In staghorn sumac, some upper stems bear clusters (panicles) of flowers that are up to 12" long and 6" across; pistillate (female) inflorescences (see below) tend to be more densely packed with flowers and smaller than the staminate (male) inflorescences. Individual flowers are 1/8-1/4" across with a five-lobed calyx, each lobe about as long as (and alternating with) the petals, and five spreading, oblong petals; both calyx and petals are yellowish-green. Staghorn sumac has a complicated sex life. Some plants have both perfect flowers (with both male and female organs) and unisexual flowers (male or female but not both) on the same individual. Other plants have flowers of only one sex (either male or female but not both). Female flowers have a central pistil with an orange-yellow, three-part stigma; male flowers have five stamens with large, bright yellow anthers. The fruits are very fuzzy, berry-like drupes about 1/4" across, deep red when ripe, each with a single seed. The velvety branches and fuzzy fruit distinguish this plant from other sumacs. A citrus-y summer drink can be made from an infusion of the fruits soaked in hot water for a few hours; just be sure to filter the infusion through a fine filter (coffee filters are good) as the hairs covering the fruit can irritate the throat. Add some sugar or honey to taste. The binomial "Rhus hirta" is occasionally used for staghorn sumac, but ITIS is clear that the accepted name is Rhus typhina.

Rhus

Rhus typhina

staghorn sumac [Blooms: May-Jul]

The tips of some short, lateral shoots of wild black currant produce clusters (racemes) of 6-15 flowers that are suspended by short pedicels from a central, drooping stalk 1-3" long. At the base of each pedicel is a 3/8" long yellowish bract. Individual flowers are 1/2" long, bell-shaped with a short tubular calyx with (1) five spreading, oblong, greenish-white apical lobes (sepals), (2) five squared-off whitish petals emerging from the tubular calyx and forming a ring-shaped wall, (3) five stamens, shorter than the petals, with cream-colored anthers, and (4) a green ovary with two styles that are fused except at their tips. The fruit consists of 3/8" wide, shiny berries, initially green, black when fully ripe, containing lots of tiny seeds. The berries are edible when cooked and have been used to make pies, jelly, or wines (if you can get to them before the birds do). Note that commercial black currants are derived from the European version of this species (Ribes nigrum), not Ribes americanum.

Ribes

Ribes americanum

wild black currant [Blooms: Apr-May]

Golden currant produces one- to three-inch-long clusters (racemes) of 5-18 drooping flowers from the leaf axils. Individual flowers are 3/4" long and across; the joined sepals are yellowish-green and tubular basally but abruptly flare into five bright golden-yellow, rectangular lobes with rounded tips. The petals are short (2-3 mm), rectangular structures that surround the throat of the corolla; they may be yellow or orange but are usually red or red-tipped. Between the petals are five stamens that extend to the tips of the petals, bearing white anthers; the styles are light green, fused to just below the stigmas, and protrude beyond the petals. The fruit is a small (1/4-3/8") edible berry with lots of seeds; fruit color is initially green but ranges from golden yellow to black when mature. Unlike gooseberries, this plant lacks spines and prickles; its large yellow flowers are distinctive. Golden currant is native to North America and was once very popular as an ornamental plant (and fruit for jams and jellies); it has probably escaped cultivation numerous times.

Ribes

Ribes aureum

golden currant [Blooms: Apr-May]

Missouri gooseberry produces groups (racemes or corymbs) of 1-3 flowers on a horizontal flower stalk near some leaf petioles; the 1/4-1/2" long flower pedicels droop downward, so the axis of the flower is vertical. An egg-shaped, sessile bract is present at the base of each flower stalk. Missouri gooseberry flowers are easy to overlook because they don't comport with one's usual idea of "flowers" — they are very elongate, as if viewed in a fun house mirror. The flowers have a very narrow, white or greenish-white, tubular calyx with 4-5 oblong, spreading or reflected sepal lobes as long as the calyx; five short, erect petals extending from the calyx; and 4-5 stamens that double the vertical length of the flower. Hidden inside, at the base of the calyx, is a smooth ovary topped by a single pistil with one style; only the style is visible externally, sometimes extending past the stamens during flowering. After fertilization, the flower parts wither and the ovary expands into a smooth, globular berry 6-12 mm in diameter containing numerous tiny seeds; the berry is initially green, turning dull red or dull purple when ripe. If you see a gooseberry in Jackson Park with a prickly surface on the fruit (looking like a miniature, green medieval mace), it is prickly gooseberry, Ribes cynosbati, which also has lobed leaves. I have yet to see prickly gooseberry in Jackson Park, but it is known to occur in northern Illinois.

Ribes

Ribes missouriense

Missouri gooseberry [Blooms: Apr-May]

The inflorescence of black locust is a drooping raceme (flower spike) 4-7" long, with a pale green central stalk (rachis) and petiole, covered in 3/4-1" long, pea-like flowers. Each flower consists of a white or light green tubular calyx with five triangular teeth, densely covered with short hairs, and five white petals — a vertical banner with a yellow spot at its base, two lateral petals forming a keel, and two more wings enclosing the keel. The stamens (with orange anthers) and a single style are hidden within the keel. The fruit is a drooping, green seedpod 2-4' long at maturity, when it is dark brown and laterally flattened, containing from 3-10, quarter-inch-long seeds. Black locust produces a hardwood that is extremely resistant to rot and was prized by boat and bridge builders, especially as a source for trenails. (A dowel used to join two pieces of wood by driving it through a slightly undersized hole bored through the pieces; see Eric Sloane, "A Reverence for Wood," p. 37.)

Robinia

Robinia pseudoacacia

black locust [Blooms: May-Jun]

The upper stems of marsh yellow-cress end in one or more 2-8" long racemes of flowers; racemes may also develop from leaf axils. Flowers in bloom are restricted to the tip of the raceme; cylindrical seedpods (siliques) oriented perpendicular to the stem decorate the lower regions of the raceme. Individual flowers are tiny (about 3 mm long) with four greenish-yellow oblong sepals, four yellow spatulate petals, 4-6 stamens with yellow or light brown anthers, and a stout style with a two-lobed stigma. After fertilization, 3-10 mm long, dumbbell-shaped, hairless, green siliques containing two rows of tiny seeds develop. The siliques bear the remnant of the style on one end and 1/2" long pedicels on the other.

Rorippa

Rorippa palustris

marsh yellow-cress [Blooms: Jun-Aug]

Prairie rose flowers arise from upper stems, either as single flowers or as groups (corymbs) of 2-4. Individual flowers are 1.5-2" across with five green, lance-shaped sepals half the length of the petals, five pink petals, a ring of numerous (~120) yellow stamens, and a button-like, flattened yellowish central cluster (the stylar disc) of short styles. The fruit is a round, 1/2" diameter rose hip, bright red when mature, with the withered remains of the five long sepals at its tip. Prairie rose prefers coarse, dry soils or sand. Prairie rose is most similar to pasture rose (Rosa carolina) but has hairless flower stalks rather than the glandular-hairy stalks of pasture rose, most flowers occur in groups of 2-4, and its leaves tend to have more leaflets (typically 9; pasture rose has 5-7).

Rosa

Rosa arkansana

prairie rose [Blooms: May-Jul]

Pasture rose flowers are usually solitary, ~2" across on pedicels covered with glandular hairs, with five bold pink (rarely white) petals, five green, pointed sepals covered with glandular hairs, ~100 bright yellow stamens, and a small yellow or yellow-orange stylar disk composed of ~40 pistils and their stigmas. The fruits are typical rose hips about 5/8" across, bright red when ripe; the glandular hairs on the pedicel and sepals persist but the sepals are deciduous and quickly fall off. The flowers are similar to purple-flowered raspberry (Rubus odoratus) but the leaves are completely different (odd-pinnate vs. palmate).

Rosa

Rosa carolina

pasture rose [Blooms: Jun-?]

Multiflora rose's flowering stalks produce abundant white flowers in panicles of up to 30 flowers — in full bloom, a multiflora rose shrub can be breathtaking. Individual flowers are about 1" across, each with five green sepals covered with glandular hairs, five oval white petals, a ring of 35-100+ stamens with bright yellow or orange anthers, and a greenish central column of styles with yellow stigmas. (The only other local species with a stylar column is climbing wild rose, Rosa setigera.) The fruit are 1/4" diameter typical rose hips, hairless, orange-red or red when mature; the sepal remnants are shed before maturity. There are at least two large multiflora rose shrubs on Wooded Island.

Rosa

Rosa multiflora

multiflora rose [Blooms: May-Jun]

Swamp rose flowers arise from the upper stems as single flowers or corymbs of 2-4 flowers. The flowers are 1.5-3" across, with five green, lance-shaped sepals, five pale- or rosy-pink, oval or heart-shaped petals, a ring of about two hundred yellow stamens, and a flat central disc of 24-50 styles that is pink or orange-red (much less often, yellow). The sepals and pedicels are covered with glandular hairs. The fruits are typical rose hips but are quite small (3/8" across, pea-sized), bright red when ripe.

Rosa

Rosa palustris

swamp rose [Blooms: May-Jun]

Rugosa rose flowers are 2-3" across; they have five sepals covered with glandular hairs, five magenta (more rarely pink or white), wrinkled petals, over 100 yellow stamens, and a yellow, flat stylar disc in the center of the flower. The fruits are typical rose hips about 1" across, bright red when ripe. Rugosa rose prefers sandy habitats and sites prone to water stress (e.g., roadsides where salt washes off the roads). The wrinkled leaves and magenta petals, profuse straight thorns/prickles, and large rose hips are distinguishing characters of rugosa rose.

Rosa

Rosa rugosa

rugosa rose [Blooms: May-Jul]

Climbing wild rose flowers are 2.5-3" across with five green sepals five times longer than wide (reflexed, then shed soon after the flowers open); five pale fuchsia to pink petals, usually with a shallow terminal notch; a ring of about 200 golden stamens; and a tall, yellow stylar column with a terminal knob in the center of the flower. (The only other local species with a stylar column is multiflora rose, Rosa multiflora.) The fruits are typical rose hips, bright red when mature, less than 1/2" wide, with no trace of the sepals.

Rosa

Rosa setigera

climbing wild rose [Blooms: Jun -Jul]

Common blackberry canes produce leaves and actively grow in their first year (primocanes); in their second year, they switch to producing flowers and fruit (floricanes). Second-year canes produce cylindrical racemes (up to 8.5' long) on the tips of short lateral shoots, longer than wide, with about a dozen flowers; the peduncles and pedicels of the raceme are covered with conspicuous glandular-tipped hairs. Each flower is 1-2" wide, has five green, pointed, triangular sepals with a tail-like extension, densely covered with glandular and non-glandular hairs; five white, rounded, wrinkled petals; 20-100 creamy stamens with white or yellow anthers; and a green cluster of numerous (100+) slender styles. After fertilization, the central cluster of styles enlarges to form a typical blackberry (drupe) 3/4" long and a bit less than half as wide, initially white or green but turning red-black when mature. The fruit is popular with most birds and mammals (including humans), who subsequently disperse the seeds.

Rubus

Rubus allegheniensis

common blackberry [Blooms: May-June]

Young, densely-hairy, stems of common dewberry terminate in single flowers or corymbs of 2-3 (rarely five) flowers. Individual flowers are 1-1.25" across consisting of five green, lance-shaped, hairy and glandular-hairy sepals with a thin, narrow "tail" at the tip; five white, wrinkled petals longer than the sepals; numerous (20-100) stamens; and a cluster of 5-150 green carpels with their club-shaped styles in the center of the flower. Floral stems may also arise from the axils of leaves. The fruits are pretty typical compound drupes (aggregate fruit like blackberries) 1/2-3/4" across, usually tightly attached to the receptacle with relatively few drupelets (10-40 of the smaller sections of the fruit); ripe fruit are dark red to black and shiny (not pruinose).

Rubus

Rubus flagellaris

common dewberry [Blooms: May-Jun]

Purple-flowered raspberry's flowers are large (up to 2-3") with five sepals densely covered with reddish glandular hairs, bluntly triangular, about half the length of the petals with long, thread-like tips; five magenta, rounded, laterally overlapping petals surrounding a compact ring of 20-100 thread-like stamens with yellow anthers; and a central mound of several hundred pale yellow, club-shaped styles. The fruit is a typical drupe, 3/4" in diameter, reddish-pink when mature, more flattened than a commercial raspberry. It can be hard to find on the plant — it is very popular with birds. Between the maple-like leaves and the showy, magenta flowers, purple-flowered raspberry is impossible to confuse with any other Rubus spp. in Illinois. Purple-flowered raspberry prefers partial shade (like woodland edges); it is critically endangered in Illinois.

Rubus

Rubus odoratus

purple-flowered raspberry [Blooms: Apr/May-Aug]

Second-year canes of Pennsylvania blackberry produce 2-4" (across) corymbs of flowers on the tips of short lateral shoots. Each flower is about one inch wide, has five green, largely hairless, lance-shaped sepals much shorter than the petals with a thin "tail" on their tips; five white, oblong, wrinkled petals, widest about a third of the way from the distal tip; 20-100 creamy stamens with white or yellow anthers; and a light green cluster of numerous (100+) styles. Lance-like stipules or large leafy bracts flank the base of the flower pedicel, the latter often partially hiding the flower. After fertilization, the central cluster of styles enlarges to form a typical blackberry (drupe) 3/4" long, initially white or green but turning black when mature. The fruit is popular with most birds and mammals (including humans), who subsequently disperse the seeds.

Rubus

Rubus pensilvanicus

Pennsylvania blackberry [Blooms: May-Jun]

Orange coneflower (aka, Sullivant's coneflower) is a short sunflower (1.5-2.5') similar to black-eyed susan but the stems are green (not red) and are sparsely (rather than very) hairy with pronounced grooves; overall orange sunflower is less hairy than black-eyed susan. The stem leaves are alternate, about twice as long as wide, up to 5" long but decreasing in size and becoming narrower up the stem; they have toothed margins, taper to a short, winged petiole (lacking in black-eyed susan), and have three main veins (one central and two submarginal). The petioles are either sessile or clasp the stem. The flowerheads are 2-3" across, produced on the apex of the stems; each flowerhead has 10-20 yellow or orange (sterile) ray florets with the petal tips notched; the numerous (50 to over 500) disk florets are tubular and dark brownish-purple with five small lobes around their upper rim and a divided style. Petals that are yellow-colored often have orange bases. This species can be highly variable.

Rudbeckia

Rudbeckia fulgida

orange coneflower [Blooms: Jul-Aug]

Black-eyed susan flowerheads are 2-3" across; they have two series (outer longer than inner) of numerous slender, sharply-pointed, green bracts beneath the flowerhead, each densely covered with long, stiff hairs; 8-20 (usually less than 12) yellow-orange, sterile ray florets (rarely with a maroon patch near the base of the petal); and 250 to over 500 dark purplish-brown disk florets, each with slender, sharply pointed styles. The fruit consists of numerous four-sided brown or black seeds that remain embedded in the remnants of the disc flowers (a gumdrop shaped, brown mass).

Rudbeckia

Rudbeckia hirta

black-eyed susan [Blooms: Jun-Oct]

Cutleaf coneflower (aka, green-headed coneflower) is an imposing tallgrass prairie plant, 3-8' tall, that can form dense stands. The composite flowerheads are 2-3" across. Eight to fifteen light green, oblong bracts lie beneath a central globe-like, light green to yellow cone surrounded by 6-12 yellow, drooping, sterile ray florets. The disk florets have yellow to yellowish green corollas and a protruding bifurcated stigma; the stamens are yellow, fused to the base of the corolla, with deep purple anthers attached around the styles side-by-side. Immature disk florets are green (thus the alternative common name); mature disk florets produce a spikey appearance. The disk florets mature from the bottom of the cone to the top, lending a pincushion-like appearance to the cone.

Rudbeckia

Rudbeckia laciniata

cutleaf coneflower [Blooms: Jul-Sep]

Sweet coneflower flowerheads are 2-3.5" across, occurring as single blooms on the tips of stems or branches. A flowerhead is comprised of numerous 1/2" long medium green, lance-shaped phyllaries, downy with short hairs; 10-20 bright yellow, oblong, sterile ray florets with a tiny notch at their tips; and a deep brown hemisphere of 200-400 disk florets (the central disc). The disk florets have a tubular, dark reddish-purple corolla; bifurcated stigmas that have sharp tips; with the purplish-brown anthers adhering side by side around the deep purple styles. Sweet coneflower is distinctive among the Jackson Park coneflowers with its chocolate brown disk and bright yellow, elongate-oval petals with a shallow notch at their tips.

Rudbeckia

Rudbeckia subtomentosa

sweet coneflower [Blooms: Jul-Aug]

Brown-eyed susan is a native bushy plant that branches at the leaf axils and produces prodigious numbers of small flowers, up to 5' tall. The stems are deep reddish brown and covered with long white hairs. The leaves are alternate, twice as long as wide, lance-shaped, up to 4" long and covered by short, stiff hairs that give it a rough texture. Some lower leaves are three-lobed, sometimes deeply, and halberd- or trident-shaped. Upper stems terminate in one or two flowerheads, 1-2" across. Each flowerhead has an underlying inner and outer series of eight (total) green bracts with hairs along the margins; 6-13 golden-yellow, sterile ray florets, often with a small notch in the tips of the oval petals; and a central cone of 150 to over 300 purplish-brown, cylindrical disc florets with five stamens and short, blunt, bifurcated stigma. If in doubt, brown-eyed susan tends to be taller than black-eyed susan, with fewer petals (6-13 vs. 8-20) and smaller flowers.

Rudbeckia

Rudbeckia triloba

brown-eyed susan [Blooms: Jun-Sep]

Hairy wild petunia is, like the name says, hairy — stems, leaves, and petioles all densely covered with long (1-2 mm) white hairs on all surfaces. The plant is short, generally 8-12" tall. The leaves are opposite, twice as long as wide, oval or triangular, with smooth margins and with short (1-3 mm) hairy petioles or sessile. The flowers emerge directly from upper leaf axils; what looks like a flower stalk is actually part of the corolla tube. The flowers are pale lavender or pale purple, about 2" across, funnel shaped with five lobes tapering rapidly to a narrow throat, four white to purplish stamens, and a white to purplish style with an asymmetrically split stigma. There are purple streaks (nectar guides) on the lowermost lobe's throat region. The short, tubular calyx is green, with five long, narrow teeth that extend for half the length of the flower; the calyx, too, is hairy. The fruit is a bullet-shaped capsule, shorter than the calyx teeth (among which it nestles); the seeds are covered with fine spiraling hairs that allow the seeds to self-bury. The flowers usually last only one day. Hairy wild petunia is a distinctive plant unlikely to be confused with any other.

Ruellia

Ruellia humilis

hairy wild petunia [Blooms: Jun-Sep]

Pale dock produces an inflorescence 4-12" long at the tip of the stem; branches in the inflorescence are few but are densely covered with numerous whorls of 10-20 small (1/8-1/4" long), green or yellow-green flowers drooping on 1/8-1/4" long pedicels. Individual flowers have six green tepals (three sepals and three similar petals) that spread at flowering to expose either six stamens or three styles, but close again after pollination. (Flowers are either pistillate (female) or staminate (male) and are wind pollinated.) After fertilization of the pistillate flowers, the fruit — a single seed in the middle of three equally-spaced wings — replaces the flower. Pale dock's seeds can persist in the soil for at least ten years.

Rumex

Rumex altissimus

pale dock [Blooms: May-Jun]

The inflorescence at the tip pf the stem in curly dock produces branching clusters with numerous whorls of 10-25 flowers dangling from slender pedicels. Flowers are tiny (1/8-1/4"), red- or yellow-green, with six tepals (three sepals and three very similar petals), three styles, or six stamens, or both; the flowers droop from a 1/4" pedicel. (The flowers are either pistillate (female), staminate (male), or perfect (both male and female organs). The flowers are wind pollinated. The tepals spread out when the flowers are mature, exposing the stamens and/or styles, then close up after pollination. The fruit is a single seed sandwiched in the center of three heart-shaped, papery membranes (derived from the tepals) set at 120° from each other, dark brown when mature. Note that more mature curly dock fruit can take on a distinct reddish tint, superficially looking like bitter dock fruit, but curly dock fruits will never show the long tooth- or finger-like projections from the edges of the wings that bitter dock exhibits.

Rumex

Rumex crispus

curly dock [Blooms: May-Jun]

The inflorescence of bitter dock is a panicle of whorled racemes up to 1' long. The greenish-red flowers droop from 1/2" pedicels. Individual flowers are 1/4" long with six tepals (six sepals and six similar petals) with pistillate (female) and male (staminate) flowers mixed in each inflorescence. Pistillate flowers have a single pistil, three styles with fringe-like, divided stigmas, and inner tepals that are (often) red; staminate flowers have six stamens and dull yellow inner tepals. After fertilization, the inner tepals of the pistillate flowers enlarge and surround an expanding, hard-shelled, three-sided seed with three membranous wings, each wing with 2-4 spiny teeth along their free edges. The fruits turn bright red as they mature.

Rumex

Rumex obtusifolius

bitter dock [Blooms: May-Jul]

Common arrowhead's flowering stalks are about as tall as the leaves, either angular or round in section. Branches of the inflorescence end in 2-5 whorls of 2-3 flowers; the terminal branch bears 3-9 whorls of 2-3 flowers. Beneath each whorl 2-3, 1/8-1/3" long, boat-shaped, green floral bracts unite. Male (staminate) flowers have 25-30 yellow stamens while female (pistillate) flowers have a central green sphere of carpels; the male flowers are located above the female flowers in each raceme. Perfect flowers (both male and female organs present) do occur but are rare. Individual flowers are about 1-1.5" across with three oval, green sepals and three rounded, white petals about twice the length of the sepals. Male flowers have 7-30 yellow stamens in the center of the flower; female flowers instead have a bur-like green cluster of hundreds of carpels and their spike-like pistils (which have terminal or lateral styles). The pistils form a dense spiral on the surface of the central green mass. After fertilization, the female flowers lose their petals and transform into a bur-like, brown fruit about 3/4" across when mature; the spikes on the bur are individual seeds (achenes) that have a large, fang-like projection at right angles to the main axis of the seed.

Sagittaria

Sagittaria latifolia

common arrowhead [Blooms: Aug – Sep]

Weeping willow is an exotic, probably originally bred in Asia or Europe. It is not very cold tolerant, so most "weeping willows" growing north of Kentucky or Virginia are actually hybrids. The aesthetically delightful "weeping" forms with yellow branches (the "golden" variety) are most likely a hybrid of Salix babylonica and Salix alba. There are separate male and female inflorescences in the form of catkins; each tree only produces one sex of catkins. The male catkins are 1-2" long and have no petals — only a series of stamens with white filaments and large (usually yellow) anthers. The female catkins are smaller (1" or less) and less showy with a series of green floral bracts that look like a series of awnings over 2-4 styles with flat stigmas; after fertilization they produce a green to brown capsule that releases cottony seeds.

Salix

Salix babylonica

weeping willow [Blooms: Apr]

Missouri River willow is dioecious — male and female florets (in the form of spike-like catkins) occur on separate plants. Catkins arise on one-year-old branches at about the same time as the leaves begin to emerge. Male catkins may be 1/2-2" long; each floret has two stamens with yellow anthers on their tips. Female catkins range from 3/4-2.5" long; the florets are yellowish-green and vase- or flask-shaped with an inflated base and a long beak that has a single protruding style. Both male and female catkins have a very small brown or bicolored bract at their bases that is covered with long, white hairs. After fertilization, female florets elongate as the catkin also elongates; the fruit is a yellowish to reddish green, hairless capsule, generally pear-shaped with a long beak. On maturity, the capsule splits to release seeds with long, attached, cottony hairs.

Salix

Salix eriocephala

Missouri River willow [Blooms: Apr]

Prairie willow is dioecious — plants produce either all male or all female inflorescences in the form of short catkins produced from one-year-old branches before the leaves emerge; a tiny black or bicolored bract covered in long, dense white hairs is present at the base of both male and female catkins. The florets lack both sepals and petals but both have a basal, hairy bract (regardless of sex). Male catkins are 1/4-1.25" long, elongating as they mature. Initially the male catkins are silvery (from long hairs) but become yellow or reddish from the numerous anthers. Individual male florets consist of a hairy, basal bract and a pair of stamens with cylindrical anthers initially purple, turning yellow, red, or orange. Female catkins are 1/2-3" long, also elongating as they mature. Individual female florets consist of the hairy bract and a hairy green ovary 4-8 mm long with an elongate beak densely covered with wooly hairs; a pair of stigmas protrude from the tip. After fertilization, the female florets transform into 1/4-1/2" long capsules, light brown at maturity, that split in two to release seeds surrounded by long, cottony hairs.

Salix

Salix humilis

prairie willow [Blooms: Apr-May]

Narrowleaf willow is dioecious — plants produce either all male or all female inflorescences (catkins) with the florets (male or female) spiraling around the catkin axis in a pseudo-whorl. Catkins are produced on one-year-old branches at the same time the leaves emerge. Male catkins are cylindrical, 3/4-2" long; they may be either erect or lean to one side but generally are ascending. Female catkins are also cylindrical, 1.5-3" long, initially green but turning light brown on maturity; they are usually terminal spikes on the new season's growth. Individual male florets consist of a single yellow, silky-hairy, oblong bract (quickly shed) and a pair of stamens with bright yellow anthers; the lower parts of the filaments are also covered by silky hairs. Individual female florets also have an oblong, basal bract that is shed; above that is a 1 mm long slender stalk supporting a bottle-shaped ovary 5-9 mm long with a pair of flat stigmas at its apex that appear to be four. After fertilization, the catkin elongates, and the ovary develops into a capsule that splits longitudinally to release the seeds when they are mature.

Salix

Salix interior

narrowleaf willow [Blooms: Apr-Jul]

Black willow is dioecious — plants produce either all male or all female inflorescences (catkins) on one-year-old branches; the catkins emerge with the leaves. Male catkins are 1-3" long, cylindrical, yellow to greenish-white, and usually curved. Female catkins are greenish are 1-3" long, elongating as they mature. Both male and female florets are numerous and arranged in pseudo whorls around the axis of their respective catkins; neither has either sepals or petals. Individual male florets have 3-6 stamens with yellow, globose anthers and a pale yellow, oval basal bract shorter than the stamens. Individual female florets also have a pale yellow, oval basal bract; a hairless, flask-shaped pistil 3-5 mm long is elevated above the bract on a 0.5-1.5 mm long (short!) pedicel and has a single style and a pair of stigmas at its tip. After fertilization, a capsule enlarges, finally splitting longitudinally to release the seeds with their attached cottony hairs.

Salix

Salix nigra

black willow [Blooms: ??]

Upper branches of elderberry end in flat to domed panicles of flowers 3-10" across. Individual flowers are about 1/4" across, with a green, cup-shaped calyx, a creamy white corolla with five petal-like lobes, five long, spreading stamens with white anthers, and a creamy white hemispherical ovary with 3-5 short styles; flowers occur in umbel-like panicles 10" across made of dozens of flowers. The fruits are <1/4" wide spherical drupes in starburst-like sprays, dark purple to black when mature. The flower stalks are light green, turning purplish as the fruit ripens. The raw fruit is sweet with a slightly bitter or astringent aftertaste but may induce nausea or diarrhea if eaten in more than small quantities. The fruit is widely used in a variety of herbal supplements (as infusions and extracts), jam, and herbal wine. Note that all parts of the plant including the sap (except the flesh of the fruit) contain toxic cyanide-producing glycosides; berries should be cooked before consumption.

Sambucus

Sambucus nigra

elderberry [Blooms: May-Jul]

Bloodroot flowers are 1.5-3" across with 8-16 (typically 8) bright white petals, numerous stamens with golden yellow anthers, and an oval, green pistil with a pale yellow, two-lobed stigma at its tip. Two light green sepals are present in the floral bud but they drop off as soon as the flower begins to open. After fertilization, the ovary expands into a spindle-shaped seed capsule about 1" long, yellow when mature, that splits to release the seeds. The seeds are disbursed by ants that are attracted by the white, fleshy appendage (an elaiosome) on the bright red seed. The red sap is highly toxic, both externally and internally — it inhibits the cellular Na+/K+ ATPase enzyme and kills the cells. Avoid getting the sap on your skin and certainly avoid getting it in your eyes or on mucous membranes.

Sanguinaria

Sanguinaria canadensis

bloodroot [Blooms: Mar-Apr]

The tips of the upper stems of Canadian black snakeroot give rise to umbels 2.5" across of greenish white flowers; each umbel usually consists of 1-4 umbellets, each with 2-3 pistillate flowers or perfect flowers and 2-6 staminate flowers. In perfect flowers, the pistils develop (and are deployed) before the stamens develop; the pistillate stage persists for much longer. Each flower has a green calyx with five lance-like lobes slightly longer than the five greenish-white petals. Male and perfect flowers add five stamens with white anthers and lack the series of hooked spines of the pistillate flowers. Female and perfect flowers have ovaries densely covered with distinctive, neatly stacked series of long, hooked bristles arrayed perpendicular to the axis of the flower. The fruit is round, 3-5 mm long, covered in rows of those same hooked bristles; it splits on maturity to release the two seeds.

Sanicula

Sanicula canadensis

Canadian black snakeroot [Blooms: Jun-Jul]

On black snakeroot, one to five 1/2" wide globoid umbels (flower clusters) arise from the tips of the upper stems. Each umbel is packed with 20-60 tiny flowers and their flower stalks (pedicels). In each umbel, 1-3 flowers are "perfect" (with both male and female organs) and the rest are staminate (stamens only). In addition to the male stamens, the perfect flowers have two long, cylindrical styles (emerging from a hidden ovary) that arch and recurve from the middle of the flower; the styles are much longer than the hooked bristles on the ovary. Both staminate and perfect flowers have a minute (<1 mm) green calyx with five rounded teeth, five dull yellow to greenish-yellow, heart-shaped petals (tip of the heart towards the center of the flower), and five protruding stamens <3 mm long with obvious yellow (or brown) anthers. The fruit is a 1/4" long round to cylindrical bur covered with short, hooked bristles; the remains of the styles often persist. The bur splits to release the two seeds inside.

Sanicula

Sanicula odorata

black snakeroot [Blooms: May-Jun]

Soapwort produces clusters of 3/4-1" flowers from the tips of terminal stems and branches. Individual flowers have a 1" long, green or reddish, sometimes hairy, cylindrical calyx; a corolla with five spreading (later reflexed), pink to white, oblong petals/lobes with a notched tip; 10 white stamens with pale yellow anthers that protrude from the throat of the flower; and a similarly protruding, divided white style. The calyx persists as an inflated seed capsule filled with 15-75 tiny dark brown, kidney-shaped seeds. Soapwort might be mistaken for a phlox, but the stamens and style in phlox are always hidden in the calyx tube, never protruding as in soapwort, and soapwort has leaves with three obvious longitudinal veins. Soapwort contains saponins in both the foliage and (especially) the seeds that make a frothy soap-like lather when boiled (and were once used as a soap substitute), but caution is recommended — the saponins are toxic. Herbivores generally avoid this plant.

Saponaria

Saponaria officinalis

soapwort [Blooms: Jun-Jul]

Hardstem bulrush's inflorescence is a branching cluster (a "pseudoumbel") at the top of the stem with an erect bract at its base that is C-shaped in section and 3/8-3.5" long; the bract appears to be a continuation of the stem. The clusters ("pseudoumbels") may be open or compact, but are more compact than in softstem bulrush. There may be 3-40 spikelets, some solitary (but never all solitary), some in groups of 2-8 at the tips of stiff floral stalks. The spikelets are reddish-brown, 10-17 mm long, cylindrical or spindle-shaped with pointed tips and with 8+ florets spirally arranged on the spikelet. The florets are perfect (both male and female parts present), each with three stamens and a two-part style; each floret is subtended by a single, 3 mm long, red-spotted scale, often with a contorted awn (both of which may be difficult to see — magnification recommended). Hardstem bulrush can tolerate standing water as much as five feet deep. You are most likely to confuse hardstem bulrush and softstem bulrush. The stem in softstem bulrush (Schoenoplectus tabernaemontani) is spongy to the touch and the pith has numerous much larger air cavities than hardstem bulrush in most of the pith. Softstem bulrush has mostly solitary spikelets, a much more open inflorescence, scales covering the florets that are usually not red-spotted, and is a lighter blue green color than hardstem bulrush's dark olive green. Softstem bulrush is much more common in Jackson Park than is hardstem bulrush.

Schoenoplectus

Schoenoplectus acutus

hardstem bulrush [Blooms: Jun-Jul]

Three-square bulrush's inflorescence is a sessile cluster of 1-5 spikelets that sit on one of the flat faces of the culm at a range of angles form ~20° to near 90°. Above the spikelets is a floral bract 2-10" long that looks like a continuation of the culm, but the side of the bract that faces the spikelets has a white-spongy appearance rather than the green of the culm or the other faces of the bract. Individual spikelets are ~1/4-1" (5-20 mm) long, conical in shape, reddish orange or brown when mature, with a chaffy surface. The midvein of the outer scales is extended to form a spiky awn that can be longer than spikelet. Each spikelet contains several perfect florets that are spirally arranged, hard to distinguish externally. Each floret has three stamens, an ovary with a single style divided into 2-3 stigmas, and a covering of chaffy scales; the stamens and stigmas are only present for a brief period before they wither and drop off. The florets are wind pollinated.

Schoenoplectus

Schoenoplectus pungens

three-square bulrush [Blooms: May-Jul]

Fertile great bulrush culms terminate in a sprawling inflorescence up to 6" long and across consisting of a number of branches and branchlets with 15-200 terminal spikelets; at the base of the branches is a single bract 1/2-3" long, C-shaped in cross section, that appears to be (but isn't) a continuation of the culm. The branches and branchlets are light green, flattened, slender, and spreading/drooping. Branchlets end in a single spikelet or a cluster of 2-5 spikelets that are sessile or have short pedicels. Spikelets are 3-17 mm (typically 6-8 mm) long, brown to reddish or orangish brown, and elongate-ovoid in shape; they may appear hairy from remnants of the withered, split styles of the florets. Each floret has a 2.5-3 mm oval brown scale at its base; the scales have a green central vein that may be extended in a short awn. The florets have three stamens and 2-3 styles (split from a single style); they are wind pollinated.

Schoenoplectus

Schoenoplectus tabernaemontani

great bulrush [Blooms: May-Jul]

Alpine squill is a 4-8" tall early spring plant, native to Eurasia. Alpine squill has two (rarely three or four) 3-6" long, narrow, curved, fleshy leaves. One to six red-brown, hairless, leafless flower stalks arise from between the basal leaves; each stalk supports 2-10 deep blue, erect flowers less than 1/2" across on individual, hairless pedicels. The basal leaves clasp the flower stalks up to about half their length. Each flower faces upwards (unlike Scilla siberica), has six spreading tepals, six stamens with dark blue anthers, and a single pistil. The stamens are distinctive in that the filaments are flattened along the flower's radial axis and taper distally; from the side they look like isosceles triangles with the anthers on their tips. Alpine squill contains cardiac glycosides; all parts of the plant are highly toxic.

Scilla

Scilla bifolia

alpine squill [Blooms: Mar-Apr]

Siberian squill is another of the early spring ephemerals native to the Caucasus and west Asia that has been wildly successful in northern Illinois and parts of Minnesota, displacing native species. Its leaves are restricted to a basal set of 2-3 leaves about 5" long and 1/4-1/2" wide, linear with a blunt tip, a shiny green surface, and smooth margins. The leaves tend to roll inward along their margins with the curl increasing towards the tip of the leaf. One or more purplish-green, 6" tall flower stalks arise from the center of the ring of basal leaves with single (rarely two or three) blue, nodding flowers on each stalk, suspended from a slender pedicel that arises directly from the unbranched flower stalks. Each flower is about 1" across with six flaring blue (rarely, white) tepals (each typically with a dark blue line down the middle), six white stamens with dark blue anthers, and a single green pistil with an undivided blue style. Siberian squill can be confused with alpine squill (Scilla bifolia), but in alpine squill the flowers face laterally or upwards rather than drooping like Siberian squill, and the flower stalks are distinctly red-brown (rather than brownish green) and branched rather than supporting flowers with a simple pedicel. Despite the common name, Siberian squill is not native to Siberia; it is native to a broad swath of western Europe from Turkey through the Caucasus and southwestern Russia. Sources differ on whether Siberian squill is toxic but note that it is avoided by vertebrate herbivores; proceed with caution.

Scilla

Scilla siberica

Siberian squill [Blooms: Mar-Apr]

At the tip of the culm, dark green bulrush produces an inflorescence comprised of one to three (rarely four or five) compound umbels of spikelets; beneath the inflorescence are 3+ leafy bracts (similar to the leaves) that are up to 1' long and 1/2" wide. At least one of the bracts is always longer than the inflorescence. The umbels generate 1/4-4" long, straight branches in all directions that terminate in umbelletes of 5-20 spikelets that rest on slender, leafy bractlets; the spikelets may be sessile or may rest on 1/2" long branchlets. The branches and branchlets are green, straight, and stiff. Spikelets are less than 1/4" long (3-6 mm), ovoid or egg-shaped, yellowish green initially but darkening to brown or black later; the spikelets are an assemblage of numerous spirally arranged, overlapping scales and their florets. The florets each have a single subtending scale, three stamens, and an ovary with a tripartite style; they are wind pollinated. Bulblets may form on one or more branches and sprout late in the season. The umbels may be visually dense and complex and take some study to sort out.

Scirpus

Scirpus atrovirens

dark green bulrush [Blooms: May-Jul]

Early figwort (aka, lanceleaf figwort) is difficult to distinguish from late- (or Maryland-) figwort (S. marilandica) except by blooming date (before July = early, after July = late, July = could be either) and details of the flowers (especially the sterile stamen). The inflorescence (a panicle) is constructed from short, spreading, sparse branches covered in glandular hairs, bearing a 3/8" long, shiny tubular flower whose outside surfaces are reddish-purple to reddish-green and inner surfaces are reddish brown (upper and lateral lobes) or greenish yellow (lower lobe). Four yellow, fertile stamens and a single blunt, slender style hug the floor of the flower, the style protruding further than the fertile stamens. A single sterile stamen (a "staminode") is located along the upper interior of the flower. The sterile stamens are yellow or green with a broad tip in early figwort (S. lanceolata); they are reddish-brown to purple and narrow in late figwort (S. marilandica). The fruit is a teardrop-shaped capsule, dark brown when mature, that splits in two longitudinally to release the numerous tiny seeds.

Scrophularia

Scrophularia lanceolata

early figwort [Blooms: May-Jul]

Late figwort's inflorescence (a panicle) gives rise to short, spreading, sparse branches covered in glandular hairs, bearing a 3/8" long, shiny tubular flower whose outside surfaces are reddish-purple to reddish-green and inner surfaces are reddish brown (upper and lateral lobes) or greenish yellow (lower lobe). Four yellow, fertile stamens and a single blunt, slender style hug the floor of the flower, the style protruding further than the fertile stamens. A single sterile stamen (a "staminode") is located along the upper interior of the flower. The sterile stamens are yellow or green with a broad tip in early figwort (S. lanceolata); they are reddish-brown to purple and narrow in late figwort (S. marilandica). The fruit is a teardrop-shaped capsule, dark brown when mature, that splits in two longitudinally to release the numerous tiny seeds.

Scrophularia

Scrophularia marilandica

late figwort [Blooms: Jul-Aug]

Mad-dog skullcap flower racemes may arise at the tips of the stems or from the axils of leaves. Each raceme is up to 6" long, containing 6-7 pairs of flowers; each flower has a short, basal leafy bract. Flowers are up to 8 mm long with a short, slender pedicel, a light green tubular calyx with two shallow lobes (the upper lobe with a dish-like projection), and a pale blue, lavender, or white, densely hairy, tubular corolla 5-8 mm long with a short, hood-like, upper lip and a slightly flared, three-lobed lower lip. Hidden inside the upper lip of the corolla are four stamens and a single bifurcated style. After fertilization, the calyx swells into a green capsule with includes the dish-like projection mentioned above, giving the capsule a unique appearance; inside is a cluster of four nutlets. The mouth of the calyx is visible as a thin slit beneath the projection.

Scutellaria

Scutellaria lateriflora

mad-dog skullcap [Blooms: Jul-Aug]

Crown vetch's flower stalks are about 6" long with a 1" wide cluster (an umbel) of 10-25 pea-like flowers on short (1/4") pedicels, all attached to the tip of the flower stalk. Each flower is 1/2" long and 1/4" wide, with a short green calyx bearing five pointed lobes and a typical pea-like corolla, bicolored in pink and white. The five petals are modified as a vertical standard (often pinker than the other petals, which are white), two lateral wings, and a pair of abutting petals forming a medial keel perpendicular to the standard. Within the keel are 10 stamens (one free and nine fused to each other, all with small yellow anthers) and a slender style, curved upwards, with a tiny terminal stigma. The fruit is a 1/2-2" long, narrow seedpod (loment) with 1-7 slightly constricted segments and a long terminal "beak" (the remains of the pistil); the pods remain attached to the flower stalk, forming a cluster often likened to "fingers". The tight flower clusters with showy, bicolored flowers are characteristic.

Securigera

Securigera varia

crown vetch [Blooms: Jun-Sep]

Biting stonecrop (aka, mossy stonecrop) is an exotic succulent that is native to Greenland and western Europe but naturalized across most of the U.S. and the lower Canadian provinces. It is a mat-forming plant with creeping stems that roots at nodes; the stems produce short, erect vegetative and flowering stems. The leaves are alternate, sessile, and densely imbricated on the erect stems; they are green or yellowish-green, with old, white leaves persisting. The succulent-like leaves are 4-5 mm long, 2.5-3 mm across, and 1.5 mm thick, convex on both the upper and underside and blunt-tipped. The inflorescence arises from the tip of one of the erect stems; it is about 5/8" (1.5 cm) long, 1/4-1.25" (5-30 mm) across, with 1-3 branches, each with 1-4 sessile (or on 1 mm long pedicels) flowers with a basal bract. The sepals closely resemble the leaves. The flowers have five bright yellow petals, typically 10 stamens with yellow anthers, and 4-5 yellow pistils, each with a single style and a pinhead-shaped stigma. The fruit is a five-pointed yellowish star of united, inflated follicles filled with numerous seeds. Biting stonecrop is not a good competitor; it grows best in thin, dry soils like cliffs, shingle, and beaches. However, it is tough — it stores water in its leaves and reportedly can go six months without external water.

Sedum

Sedum acre

biting stonecrop [Blooms: Jun]

The tips of the upper stems of common groundsel produce dense clusters of flowerheads on short peduncles; inflorescences can also arise from leaf axils. Common groundsel flowerheads are cylindrical, 8 mm long and 4 mm across, with black-tipped, green bracts around the outside at both the base and the apex and 13-80 yellow disc florets peeking out the end; mature flowerheads are easily mistaken for flower buds. The disc florets have tubular yellow corollas, five stamens fused to the upper part of the corolla with yellow-brown anthers, and a bifurcated style with purplish stigmas. There are no ray florets. This is an easy plant to overlook. The flowerheads are twice as long as wide. The seedhead looks like a compact dandelion tuft with seeds on parachutes of light brown hairs.

Senecio

Senecio vulgaris

common groundsel [Blooms: May-Jul]

The five petals and five sepals of Maryland senna's 3/4" flowers are both yellow. The single pistil has many spreading white hairs and arches upward. The anthers of the 10 stamens are a striking dark brown (like partridge pea). The upper three stamens have short filaments and short anthers that produce only sterile pollen (as a pollinator reward). The middle four stamens have short filaments and long anthers while the lower three stamens have long filaments and long anthers; all seven of these stamens produce fertile pollen that is released by "buzz pollination." The flowers do not produce nectar. The fruit is a flattened seedpod 1/2" across and 3-4" long with 10-18 segments, each containing a single 1/4" flattened seed.

Senna

Senna marilandica

Maryland senna [Blooms: Jul]

Flower buds arise singly or in small groups on 1/2" long peduncles from the leaf axils. Because the flower peduncles are shorter (1/2") than the leaf petioles (1"), the flowers are often partly hidden among the leaves. Individual flowers are about 8 mm across. A flower contains five green, triangular sepals; five light yellow or light orange, rounded, floppy petals with pale lines that function as nectar guides and asymmetrical tips; and a central reproductive column (like mallows, to which prickly sida is related). That column consists of five styles fused along most of their lengths, each with a globose terminal stigma, and numerous stamens with yellow anthers. After fertilization, a circular seedpod forms from the five carpels; when mature, the seedpod turns brown and breaks into five segments, each containing a single reddish-brown, three-angled seed.

Sida

Sida spinosa

prickly sida [Blooms: Aug-Sep]

Evening campion is an exotic from Europe that grows to be 2-3' tall. It is nominally a night-blooming species, but I've observed it in bloom throughout the day in shady areas. Male and female plants are separate. The upper stems end in clusters of one or more 1-1.5" long flowers. The "bladder" (the calyx) is covered with a fuzz of fine hairs and has dark green or reddish-purple lines running from pole to pole (10 lines in male flowers, 20 in female). The five petals are heart shaped (with the point towards the center of the flower) and are deeply cleft into two lobes; the petals form a fringe that makes a distinct collar around the opening to the floral tube. Female flowers have five emergent styles (rarely four or six); male flowers have 10 yellow stamens that barely emerge from the collar at the center of the flower. (Other local Silene sp. have three styles.) The fruit is brown, urn-shaped, and has 10 small teeth on the distal end (or five pairs if you prefer). (Five or six teeth total in S. noctiflora, S. stellata, and S. vulgaris.) Evening campion evolved a dioecious life history (separate male and female plants) about 11 million years ago. (Other species in the genus have "perfect" flowers with both male and female organs present and functional in the flowers.) The evolution and genomic history of the sex-determining Y chromosome (XX = female, XY = male) has been of considerable interest for the light it shines on the evolution of Y chromosomes in both plants and animals (Moraga et al. 2025. Science 387:630–636; Akagi et al. 2025. Science 387:637–643).

Silene

Silene latifolia

evening campion [Blooms: May-Aug]

Royal catchfly's bright red flowers are restricted to the upper regions of the plant as clusters arising from the tips of stems. Individual flowers are 3/4-1" across, have an elongate (1"), narrow, cylindrical calyx with 10 longitudinal ridges, five narrow red or scarlet petals that flare from the tip of the calyx, and stamens with gray anthers that protrude well beyond the opening to the calyx. There are three corkscrew-shaped, threadlike styles that develop after the stamens have matured; like the stamens, they protrude well outside the calyx opening. The fruit is a 1/2" long capsule, open at the top, with 6-8 spreading teeth around the lip. Royal catchfly is hummingbird and butterfly pollinated.

Silene

Silene regia

royal catchfly [Blooms: Jul-Aug]

Starry campion's main stem ends in a panicle of flowers up to 8" long and 3-4" across; additional panicles may arise on the lateral stems on robust plants. Flowers occur in groups of 2-3 on the ends of long, slender branches; the flowers rest directly on short (1/4") pedicels. Individual flowers are 3/4" across. Each flower consists of a bell shaped, light green, fuzzy calyx nearly as broad as it is long with five broad, triangular teeth on its free end; five white petals with a narrow base and a "fringe" of 8-12 narrow lobes on their free ends; 10 stamens with slender white filaments that extend well outside the throat; and three white styles. The styles emerge from a large, green, globular ovary in the middle of the flower. After fertilization, the calyx gets broader (nearly triangular in profile) as the ovary expands into a spherical green ball; the fruit is brown, urn-shaped, and has six teeth on the distal end. The flowers tend to close in bright midday light. They are usually pollinated by moths and, to a lesser extent, bumblebees.

Silene

Silene stellata

starry campion [Blooms: Jun-Jul]

Rosinweed produces a panicle of sunflower-like blooms from the top of the stem and the tops of side stems (if any). Individual flowerheads are 2-3" across; they consist of 12-35 yellow, pistillate (female) ray florets and 70-200+ functionally male disc florets. The green bracts beneath the flowerheads are teardrop-shaped, partially overlapping in two or three layers, and sometimes covered with glandular hairs. The petals of the ray florets have two prominent longitudinal grooves and a tiny apical notch. Only the ray florets can produce seeds — a split style protrudes from a short tube at the base of the ray floret. The central disk is initially green but becomes yellow as the disk florets open; they are yellow, tubular, with five triangular lobes at their free end, with a column of brown stamens with the tips of very long, (non-functional) styles protruding from the tubular corolla. The fruit is a flat seed that develops from the ray florets. (The curious arrangement where only the ray florets can produce seeds while the disk florets are functionally male is true throughout the genus Silphium. The opposite is true in the true sunflowers, genus Helianthus.)

Silphium

Silphium integrifolium

rosinweed [Blooms: Jul-Sep]

Compass plant flower stalks are very hairy, have scattered sessile, triangular bracts, extend vertically multiple feet, and bear 3-4" yellow, sunflower-like composite flowers. There are 20-35 yellow ray florets (e.g., petals) and 100-200+ yellow, tubular disk florets. Behind the flowerheads are two or three layers of very hairy, green, lance-like bracts with sharply pointed, recurved tips. For unknown reason (it just IS), only the ray florets are fertile; the disc florets bear only functional stamens (with a non-functional style protruding through the middle of the stamen). (True throughout the genus Silphium. The opposite is true in the sunflowers, genus Helianthus, where the ray florets are functionally male and the disk florets are fertile, functional females.)

Silphium

Silphium laciniatum

compass plant [Blooms: Jun-Sep]

A cup plant may have 10-30 flowerheads in bloom at one time. Behind the flowerhead are two or three layers of green bracts; the outer layer is egg shaped with a triangular, pointed, recurving tip. Each sunflower-like flowerhead is about 3-4" across; it has 18-40 yellow ray florets (e.g., the petals) and 85-150 yellow disk florets. The ray florets have a bifurcated but functional style protruding from a short yellow tube at the base of the petal; the disc florets are initially green but transform into yellow, tubular corollas with a non-functional style protruding through the fully-functional stamen. (True throughout the genus Silphium. The opposite is true in the sunflowers, genus Helianthus, where the ray florets are functionally male and the disk florets are fertile, functional females.) The cup-like leaves and square stem distinguish cup plants from other prairie wildflowers.

Silphium

Silphium perfoliatum

cup plant [Blooms: Jul-Sep]

Prairie dock's hairless flower stalks produce a panicle of buds and flowerheads. The flowerheads are 2-3" across, with 15-30 bright yellow ray florets with pointed tips and two grooves running the length of the petals; a yellow central disc about 1/4-1/3 the width of the flower contains 120-140 disk florets, green when still buds but bright yellow when open. Behind the flowerhead are two or three layers of green, egg or teardrop shaped, hairless bracts. The ray florets have a bifurcated but functional style protruding from a short yellow tube at the base of the petal; the disc florets have tubular corollas with a non-functional style protruding through the stamen. (True throughout the genus Silphium. The opposite is true in the sunflowers, genus Helianthus, where the ray florets are functionally male, and the disk florets are fertile, functional females.)

Silphium

Silphium terebinthinaceum

prairie dock [Blooms: Jun-Sep]

Wild mustard's upper stems end in racemes of 1/2" wide yellow flowers. Each flower has four yellow petals, six yellow stamens, and a single green pistil. After fertilization, the pistil elongates into a thin, cylindrical silique (seedpod), 1/2-1.5" long, filled with tiny (2 mm diameter) brown or black seeds; the distal third of the silique is a ridged or square "beak". The seeds are reported to remain dormant but viable in the soil for up to 60 years.

Sinapis

Sinapis arvensis

wild mustard [Blooms: May-Jun]

Hedge mustard flowers occur at the tips of long, slender flower stalks that curve upward; the flower stalks typically arise in abundance at the top of the plant. Each flower is small (1/4" across) with four greenish-yellow sepals, four rectangular yellow petals with rounded tips, a single stout style, and six stamens. The fruit is a very slender, cylindrical seedpod (silique) lower on the flower stalk than the blooming flowers; the siliques are 3/8-3/4" long, erect, oriented parallel to and often appressed to the flower stalk, with the remains of the style on their tips. The siliques turn light brown when mature and split open to release the seeds. The short (<3/4"), straight, appressed seedpods and the upward-curving, sparse flower stalks with only a few blooms open at any one time distinguish hedge mustard from other local mustards.

Sisymbrium

Sisymbrium officinale

hedge mustard [Blooms: May-Jul]

White blue-eyed grass is a native perennial, 6-12" tall with a tuft of basal leaves and flowering stalks that are grass-like (if you squint). The basal leaves are green, 1/8" across, and strap-like; they are shorter than the flowering stalks. The flowering stalks are weakly winged and have a pair of sessile spathes (bracts sheltering the inflorescence) at their tips. The spathes consist of a pair of 1" long reddish or light brownish green bracts backed by a 3" long leafy bract; an umbel of up to six flowers arises between the bracts but only one or two flowers are in bloom at any given time. Each flower is only about 1/2" across and is supported by a 1/2" long pedicel. The flower consists of six white or pale blue tepals with a yellow patch at their bases and narrow, dagger-like tips; a column of yellow or orange-yellow stamens fused along their length almost to the anthers; and a globoid, green ovary covered with fine hairs and sporting a style with three slender lobes. Fertilized flowers produce a ridged, globoid seed capsule, initially green but turning tan to brown as it matures.

Sisyrinchium

Sisyrinchium albidum

white blue-eyed grass [Blooms: May-?]

Water parsnip's upper stems end in 2-5" wide, flat-topped umbels of flowers with numerous (10-20) umbellets, each with 20-35 tiny (1/8" wide) flowers. At the base of the umbel are 6-10 narrow bracts that are curved down towards the stem. Each flower has a 3-5 mm long stalk; a short, light green calyx; five white, heart-shaped petals with incurved tips; five stamens that extend well outside the flower; and an ovary with two diverging styles. The fruits are 3 mm long, slightly laterally compressed, oblong, with strong ribbing; each fruit contains exactly two seeds.

Sium

Sium suave

water parsnip [Blooms: Jul-Aug]

Horsenettle's upper stems end in small clusters of 3/4" wide white or light violet flowers with wavy petal margins and hairy pedicels; clusters may also arise from leaf axils. Each flower has a green, hairy calyx with five lobes that taper gradually to sharp tips (typically slightly reflexed); five triangular petals that are fused at their bases; and five yellow, banana-shaped anthers 6-9 mm long surrounding a long, slim, light green style with a darker green, globular terminal stigma. After fertilization, the ovary expands into mature berries about 1/2" in diameter, initially green-striped, that look like yellow cherry tomatoes when mature; they are half enclosed in a papery derivative of the calyx.

Solanum

Solanum carolinense

horsenettle [Blooms: Jun-Aug]

Bittersweet nightshade flowers occur in small (6-12 flowers) clusters arising from the stems and leaf axils. Each flower is about 3/8" across consisting of a small green, purple, or brown calyx with five shallow, triangular lobes; five petals, purple with paired yellow or green spots at their bases, that flare or are reflected backwards over the base of the flower; five bright yellow anthers 4.5-6 mm long that are appressed to form a tight cylinder; and a single green, slender style closely surrounded by the anthers and protruding beyond them. The fruit is a 3/8-1/2" long, oval, tomato-like berry, initially green; mature berries are bright red. The foliage and fruit contain the alkaloid solanum and are toxic; fatalities are rare but have occurred. Horse nettle (S. carolinense) is similar to bittersweet nightshade but has numerous sharp bristles and spines on the stems and leaves that are lacking in bittersweet nightshade. Black nightshade (S. ptycanthum) is also similar but has black (rather than red) mature fruits and white (not purple) petals on the flowers.

Solanum

Solanum dulcamara

bittersweet nightshade [Blooms: May-Aug]

Black nightshade produces solitary umbels 3/4" long usually, from the axils of middle and upper leaves; the flower pedicels are about 3/8" long. Flowers are 1/4-3/8" across consisting of five sepals partially fused at the base of the flower; five white petals, green at their base, sometimes with purple highlights on the outside of the petal, and usually curved backwards; five anthers and their thick filaments appressed to form a tight, bright yellow cylinder with a yellowish-green stem; and a slender style running up the center of the appressed anthers to just emerge from the tip as a green stigma. The fruit is a 1/4-3/8" tomato-like berry, initially green; mature berries are black. The foliage and unripe fruit contain the alkaloid solanum and are toxic.

Solanum

Solanum ptychanthum

black nightshade [Blooms: Jul-Sep]

Tall goldenrod flower clusters vary from pyramidal (at least as long as wide, the most common) to club shaped; the tip of the pyramidal form is often arched or nodding (like a bent topknot). The flowerheads are less than 1/4" across, have 8-15 yellow ray florets and 3-6 yellow disc florets; the base of the flowerheads have 2-3 layers of narrow, hairless, greenish bracts (phyllaries) always more than 3 mm long in total. The flowerheads are all attached on one side of the hairy floral stalks. The fruit is a dry seed with a tuft of white hairs (a pappus); it is 2.5-3.5 mm long. Tall goldenrod is difficult to differentiate from Canada goldenrod (S. canadensis) (both are three-nerved) but tall goldenrod has phyllaries longer than 3 mm while Canada goldenrod's phyllaries are always shorter than 3 mm. Some argue the two may be the same species, but tall goldenrod blooms later than Canada goldenrod. Both tall goldenrod and late goldenrod (Solidago gigantea) are three-nerved, have the largest leaves at mid-stem, and pyramidal inflorescences, but tall goldenrod has rough-feeling (sandpapery) stems and leaves while late goldenrod has smooth stems and leaves. Of the three very similar species (late goldenrod, tall goldenrod, and Canada goldenrod), only late goldenrod has a hairless stem.

Solidago

Solidago altissima

tall goldenrod [Blooms: Sep-Oct]

The axils of the middle and upper leaves of woodland goldenrod produce small clusters of 1-12 flowerheads; the stem tip may also develop a small (3" long, 1.5" across) panicle of flowerheads. Individual flowerheads are tiny (3 mm) consisting of 4-5 ray florets with yellow, oblong-elliptical "petals" and 3-6 disc florets with golden yellow, tubular corollas with five tiny lobes. At the base of each flowerhead are three overlapping series of light green, elongate-elliptical bracts (phyllaries). The fruit is a small, bullet-shaped seed 1-2 mm long with a tuft of white hairs 3-5 mm long. In Illinois, only woodland goldenrod and broad-leafed goldenrod (Solidago flexicaulis) produce clusters of flowerheads from the axils of the middle and upper leaves; however, the latter has coarsely serrated leaves with petioles and should be easy to distinguish from woodland goldenrod.

Solidago

Solidago caesia

woodland goldenrod [Blooms: Sep-Oct]

A panicle of flowering stems develops at the top of a Canada goldenrod plant; the flowering stems arch away from the main stem, their upper sides covered with yellow flowers. The panicle may be pyramidal (at least as long as wide) to spreading (wider than long); it is sometimes club-shaped on smaller plants. Individual flowers are 1/8-1/4" across, with 8-14 yellow ray flowers and 3-6 yellow disc flowers. The base of the flower is surrounded by 3-4 layers of narrow, hairless, green bracts (phyllaries); the entire set of phyllaries is two to less than three millimeters long. The flower stalks (pedicels) are hairy, about as long as the set of phyllaries, and curve upwards. The fruit is a dry, ribbed seed 1-1.5 mm long with a tuft of white hairs 1.8-2.2 mm long. Canada goldenrod is difficult to differentiate from tall goldenrod (S. altissima) (both are three-nerved), but tall goldenrod has phyllaries longer than 3 mm while Canada goldenrod's phyllaries are always shorter than 3 mm. Some argue the two may be the same species but tall goldenrod blooms later than Canada goldenrod. Of the three very similar species (late goldenrod, tall goldenrod, and Canada goldenrod), only late goldenrod has a hairless stem.

Solidago

Solidago canadensis

Canada goldenrod [Blooms: Jul-Oct]

The tip of broad-leaved goldenrod's stem produces a cylindrical inflorescence (a raceme or a narrow panicle) 1.5-5" long and about a third as wide; smaller racemes (1/2-1.5" long, smaller than the leaves) arise from the axils of the upper leaves. Individual flowerheads are about 1/4" across with 3-4 yellow ray florets asymmetrically deployed around the flowerhead and 4-8 yellow disk florets. The base of the flowerhead is surrounded by 3-5 series of unequal, narrowly oblong, light green phyllaries; the outermost phyllaries are 1-2 mm long while the innermost are 3.7-4.7 mm long. Broad-leaved goldenrod prefers high-quality, moist, shaded woodlands. In Illinois, only broad-leaved goldenrod and woodland goldenrod (Solidago caesia) produce clusters of flowerheads from the axils of the middle and upper leaves. Broad-leaved goldenrod has unusually large flowers for a goldenrod and the ray florets are not evenly distributed around the flowerhead. In addition, woodland goldenrod has smooth or finely serrated leaf margins (rather than coarsely-toothed leaves) and no petioles (the leaves are sessile) — it should be easy to distinguish from broad-leaved goldenrod.

Solidago

Solidago flexicaulis

broad-leaved goldenrod [Blooms: Jul-Sep]

The central stem of late goldenrod gives rise to an inflorescence (a panicle) up to one foot long and wide made up of light green, slightly fuzzy, recurved branches with a few leafy bracts smaller than the stem leaves. Each flowerhead is about 1/4" across with 9-15 yellow ray florets and 7-12 yellow disk florets. Surrounding the base of the flowerhead are 2-5 series of appressed bracts (phyllaries) that combined are 2-4+ mm long; individual bracts are elongate lance-shaped. The flower stalks (pedicels) are minutely hairy, usually shorter than the phyllaries, all attached to one side of the panicle branches and curving upwards. Full-sized late goldenrod plants are imposing — tall, green or reddish-brown, yellow-tipped columns towering over every plant around them. The leaves of late goldenrod are similar to those of Canada goldenrod (S. canadensis), but the latter has hairy stems and tends to be somewhat shorter. Both tall goldenrod (S. altissima) and late goldenrod are three-nerved, have the largest leaves mid-stem, and pyramidal inflorescences, but tall goldenrod has rough-feeling (sandpapery) stems and leaves while late goldenrod has smooth stems and leaves. Of the three very similar species (late goldenrod, tall goldenrod, and Canada goldenrod), only late goldenrod has a hairless stem.

Solidago

Solidago gigantea

tall goldenrod [Blooms: Jul-Sep]

Early goldenrod's inflorescence is apical, a panicle of flowering stems that "often arch upward and outward like a fireworks display" (John Hilty, www.illinoiswildflowers.info). Individual flowerheads are about 1/4" across; they have 4-12 yellow ray florets, not all open at one time, and 8-15 yellow disk florets. The base of the flowerhead is surrounded by 3-4 series of overlapping, narrow, hairless, yellowish-green bracts (phyllaries) that together are 3-4 mm (1/16") long. The pedicels (flower stalks) are usually hairless, all attached on one side of the panicle's flowering branches and curving upward. The fruit is a cone-shaped dry seed 1-1.5 mm long with an attached tuft of light brown hairs 2.5-3.5 mm long. The combination of wing-like leaflets in the leaf axils, hairless stems and leaves, and an inflorescence whose flowering stems flare up and out is diagnostic for early goldenrod. Field goldenrod (Solidago nemoralis) is much the same size and general appearance, but has hairy stems and leaves, unlike early goldenrod.

Solidago

Solidago juncea

early goldenrod [Blooms: Jul/Aug-?]

The wand-shaped, nodding inflorescence of field goldenrod arises from the tip of the stem; it is 3-7" long and widest in the middle, tapering towards either end; the flowerheads are all on one side of the flower branches. Flowerheads are each 1/4" across consisting of 4-10 yellow ray florets and 3-10 yellow disk florets. The bracts (phyllaries) surrounding the base of the flowerhead are in three overlapping series; they are pale greenish yellow, covered in short, white hairs. The fruit is a dry seed 0.5-2 mm long with an attached tuft of light brown hairs. Field goldenrod can be distinguished from other goldenrods by (1) its diminutive size, (2) the inflorescence that nods to one size, (3) leaflets present in leaf axils (4) short, fine hairs on both leaves and stems, and (5) the grayish cast of the leaves.

Solidago

Solidago nemoralis

field goldenrod [Blooms: Aug-Oct]

Upland white goldenrod stems end in a flat-topped panicle 6" across of flowerheads; colonies can present a visually continuous surface of flowers. The flowerheads are 3/4-1" across on 1" stems; each flowerhead has 10-25 white, pistillate ray florets (no stamens) and 30-36 yellowish, perfect disc florets (with both pistils and stamens). The petal-like rays are bright white and spreading, sometimes with notched tips; they look very much like a generic aster flowerhead. The disk florets are dull white and tubular; the five stamens in each disk floret are conjoined and yellow, giving a yellowish cast to the disk. Behind the flowerhead are 4-5 series of hairless bracts (phyllaries), light green at their base, darker green at the tips, each phyllary with a prominent light green mid-vein; the phyllaries are 4 mm long in total. Upland white goldenrod is uncommon in most of northern Illinois except in the sandy soils near Lake Michigan. ITIS and the Flora of North America accept Solidago ptarmicoides as a valid species name; the USDA Plants Database and NatureServe Explorer consider S. ptarmicoides as a junior synonym of Oligoneuron album (as does illinoiswildflowers.info).

Solidago

Solidago ptarmicoides

upland white goldenrod [Blooms: Aug-Sep]

Stiff goldenrod's inflorescence (a corymb) arises from the tip of the main stem and from the upper side stems. It is a compact, flat-topped or rounded mass of flowers 2-5" wide. Each flower is 3/8" across (big for a goldenrod) with 6-13 yellow, pistillate ray florets (with purple styles and no stamens) and up to 35 (usually fewer) yellow, perfect disc florets with five yellow stamens and a purplish, split style. The back of the flowerhead is covered with 3-5 series of overlapping bracts (phyllaries) with the midvein and other veins visible. The fruit is a dry seed that is angular in outline, about 2 mm long with a tuft of white or light brown hairs. The distinctive stiff, rounded upper leaves that clasp the stem are all you need to unequivocally identify stiff goldenrod.

Solidago

Solidago rigida

stiff goldenrod [Blooms: Aug-Oct]