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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-?]

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-?]

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]

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]

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]

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-?]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]