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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]

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]

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]

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?]

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]

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]

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]

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]

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]

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]

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]

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]

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]