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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]

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]

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]

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]

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]

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]

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]

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]

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]

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: ?]

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: ??]