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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]

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]

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]

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]

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]

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]