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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]

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]

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]

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-?]

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]

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]

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-?]

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]

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]

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]

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]