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In buckthorn, umbels of flowers arise from leaf axils. Flowers on a single plant may be perfect (both male and female organs present), but more commonly the flowers are dioecious with either all male (staminate) or all female (pistillate) flowers found on any given plant. Individual flowers are 1/4" across. They have four greenish-yellow, triangular, spreading sepals that together form a calyx and four petals that can't be easily seen without magnification; the "petals" in the flowers are actually sepals. Male flowers have four greenish stamens with cream-colored anthers; female flowers have a single style that has a tip divided into four branches. After fertilization, female (or perfect) flowers produce a shiny black, 1/4" wide, cherry-like fruit containing 3-4 seeds. Birds can eat the fruit without ill effects, but in humans the fruit produces stomach cramps and acts as a strong laxative (as indicated by the species name, "cathartica").

Rhamnus

Rhamnus cathartica

buckthorn [Blooms: May-Jun]

Jetbead flowers are solitary, arising on the tips of the green twigs. Flowers are elevated on 1/4-1/2" long stalks. There are four green sepals at the base of the flower, each with a bractlet half the length of the sepals that is located below the intersection of each pair of sepals. Four white, nearly circular petals alternate in position with the sepals. A greenish hypanthium covers the center of the flower with a four-lobed ridge marking its edges. Numerous (30-60) stamens with white filaments and yellow anthers, usually in four distinct clusters, lie inside the ridge; the stamens surround four pistils, each with a single style and a circular, terminal stigma. After fertilization, 1-4 fruits develop in the center of the flower that turn shiny black at maturity (the "jetbead"); the seeds remain attached to the persistant sepals until late in the fall and may persist through the winter.

Rhodotypos

Rhodotypos scandens

jetbead [Blooms: Apr-May]

Upper branches of elderberry end in flat to domed panicles of flowers 3-10" across. Individual flowers are about 1/4" across, with a green, cup-shaped calyx, a creamy white corolla with five petal-like lobes, five long, spreading stamens with white anthers, and a creamy white hemispherical ovary with 3-5 short styles; flowers occur in umbel-like panicles 10" across made of dozens of flowers. The fruits are <1/4" wide spherical drupes in starburst-like sprays, dark purple to black when mature. The flower stalks are light green, turning purplish as the fruit ripens. The raw fruit is sweet with a slightly bitter or astringent aftertaste but may induce nausea or diarrhea if eaten in more than small quantities. The fruit is widely used in a variety of herbal supplements (as infusions and extracts), jam, and herbal wine. Note that all parts of the plant including the sap (except the flesh of the fruit) contain toxic cyanide-producing glycosides; berries should be cooked before consumption.

Sambucus

Sambucus nigra

elderberry [Blooms: May-Jul]

Evening campion is an exotic from Europe that grows to be 2-3' tall. It is nominally a night-blooming species, but I've observed it in bloom throughout the day in shady areas. Male and female plants are separate. The upper stems end in clusters of one or more 1-1.5" long flowers. The "bladder" (the calyx) is covered with a fuzz of fine hairs and has dark green or reddish-purple lines running from pole to pole (10 lines in male flowers, 20 in female). The five petals are heart shaped (with the point towards the center of the flower) and are deeply cleft into two lobes; the petals form a fringe that makes a distinct collar around the opening to the floral tube. Female flowers have five emergent styles (rarely four or six); male flowers have 10 yellow stamens that barely emerge from the collar at the center of the flower. (Other local Silene sp. have three styles.) The fruit is brown, urn-shaped, and has 10 small teeth on the distal end (or five pairs if you prefer). (Five or six teeth total in S. noctiflora, S. stellata, and S. vulgaris.) Evening campion evolved a dioecious life history (separate male and female plants) about 11 million years ago. (Other species in the genus have "perfect" flowers with both male and female organs present and functional in the flowers.) The evolution and genomic history of the sex-determining Y chromosome (XX = female, XY = male) has been of considerable interest for the light it shines on the evolution of Y chromosomes in both plants and animals (Moraga et al. 2025. Science 387:630–636; Akagi et al. 2025. Science 387:637–643).

Silene

Silene latifolia

evening campion [Blooms: May-Aug]

Royal catchfly's bright red flowers are restricted to the upper regions of the plant as clusters arising from the tips of stems. Individual flowers are 3/4-1" across, have an elongate (1"), narrow, cylindrical calyx with 10 longitudinal ridges, five narrow red or scarlet petals that flare from the tip of the calyx, and stamens with gray anthers that protrude well beyond the opening to the calyx. There are three corkscrew-shaped, threadlike styles that develop after the stamens have matured; like the stamens, they protrude well outside the calyx opening. The fruit is a 1/2" long capsule, open at the top, with 6-8 spreading teeth around the lip. Royal catchfly is hummingbird and butterfly pollinated.

Silene

Silene regia

royal catchfly [Blooms: Jul-Aug]

Starry campion's main stem ends in a panicle of flowers up to 8" long and 3-4" across; additional panicles may arise on the lateral stems on robust plants. Flowers occur in groups of 2-3 on the ends of long, slender branches; the flowers rest directly on short (1/4") pedicels. Individual flowers are 3/4" across. Each flower consists of a bell shaped, light green, fuzzy calyx nearly as broad as it is long with five broad, triangular teeth on its free end; five white petals with a narrow base and a "fringe" of 8-12 narrow lobes on their free ends; 10 stamens with slender white filaments that extend well outside the throat; and three white styles. The styles emerge from a large, green, globular ovary in the middle of the flower. After fertilization, the calyx gets broader (nearly triangular in profile) as the ovary expands into a spherical green ball; the fruit is brown, urn-shaped, and has six teeth on the distal end. The flowers tend to close in bright midday light. They are usually pollinated by moths and, to a lesser extent, bumblebees.

Silene

Silene stellata

starry campion [Blooms: Jun-Jul]

Rosinweed produces a panicle of sunflower-like blooms from the top of the stem and the tops of side stems (if any). Individual flowerheads are 2-3" across; they consist of 12-35 yellow, pistillate (female) ray florets and 70-200+ functionally male disc florets. The green bracts beneath the flowerheads are teardrop-shaped, partially overlapping in two or three layers, and sometimes covered with glandular hairs. The petals of the ray florets have two prominent longitudinal grooves and a tiny apical notch. Only the ray florets can produce seeds — a split style protrudes from a short tube at the base of the ray floret. The central disk is initially green but becomes yellow as the disk florets open; they are yellow, tubular, with five triangular lobes at their free end, with a column of brown stamens with the tips of very long, (non-functional) styles protruding from the tubular corolla. The fruit is a flat seed that develops from the ray florets. (The curious arrangement where only the ray florets can produce seeds while the disk florets are functionally male is true throughout the genus Silphium. The opposite is true in the true sunflowers, genus Helianthus.)

Silphium

Silphium integrifolium

rosinweed [Blooms: Jul-Sep]

A cup plant may have 10-30 flowerheads in bloom at one time. Behind the flowerhead are two or three layers of green bracts; the outer layer is egg shaped with a triangular, pointed, recurving tip. Each sunflower-like flowerhead is about 3-4" across; it has 18-40 yellow ray florets (e.g., the petals) and 85-150 yellow disk florets. The ray florets have a bifurcated but functional style protruding from a short yellow tube at the base of the petal; the disc florets are initially green but transform into yellow, tubular corollas with a non-functional style protruding through the fully-functional stamen. (True throughout the genus Silphium. The opposite is true in the sunflowers, genus Helianthus, where the ray florets are functionally male and the disk florets are fertile, functional females.) The cup-like leaves and square stem distinguish cup plants from other prairie wildflowers.

Silphium

Silphium perfoliatum

cup plant [Blooms: Jul-Sep]

Early goldenrod's inflorescence is apical, a panicle of flowering stems that "often arch upward and outward like a fireworks display" (John Hilty, www.illinoiswildflowers.info). Individual flowerheads are about 1/4" across; they have 4-12 yellow ray florets, not all open at one time, and 8-15 yellow disk florets. The base of the flowerhead is surrounded by 3-4 series of overlapping, narrow, hairless, yellowish-green bracts (phyllaries) that together are 3-4 mm (1/16") long. The pedicels (flower stalks) are usually hairless, all attached on one side of the panicle's flowering branches and curving upward. The fruit is a cone-shaped dry seed 1-1.5 mm long with an attached tuft of light brown hairs 2.5-3.5 mm long. The combination of wing-like leaflets in the leaf axils, hairless stems and leaves, and an inflorescence whose flowering stems flare up and out is diagnostic for early goldenrod. Field goldenrod (Solidago nemoralis) is much the same size and general appearance, but has hairy stems and leaves, unlike early goldenrod.

Solidago

Solidago juncea

early goldenrod [Blooms: Jul/Aug-?]

Saltmarsh sand-spurry flowers consist of five elliptical green sepals, five white to pink petals slightly longer than the sepals, 2-5 stamens with bright yellow anthers, and three short (0.7 mm), thread-like styles and three stigmas. In the Great Lakes region, saltmarsh sand-spurry is widely present along roads where salt is used as a deicer. Some sources refer to this plant as Spergularia marina, but ITIS rejects that binomial; Spergularia salina is the accepted name.

Spergularia

Spergularia salina

saltmarsh sand-spurry [Blooms: May-Aug]

Common chickweed's flower stems arise from the axils of outer pairs of leaves; the flower stems terminate in small cymes of flowers. Individual flowers are about 1/4" across, consisting of five green sepals longer than the petals, tapering to a point, hairy on the outside; five white, widely-spaced, bifid (deeply notched, each appearing double) petals; 2-10 (usually 3-5) stamens with reddish-violet anthers; and a central green ovary with three styles fused except at their flaring tips. The fruits are light brown, cylindrical, 4-6 mm long seed capsules nestled in the embrace of the (hairy) sepals with six small teeth around their upper ends. Common chickweed is usually self-pollinating (autogamous) but is occasionally cross-pollinated by flies. Chickweeds of the genus Stellaria (like common chickweed) have three styles; chickweeds of the genus Cerastium (like mouse-eared chickweed) have five styles. The flowers of whitlow-grass (Draba verna) are superficially similar to common chickweed in size and color but have only four bifid petals rather than five. One odd (but distinguishing) characteristic of common chickweed — if you bend the stem back and forth, the epidermis and parenchyma will split, leaving a central vascular bundle which will stretch elastically if you then pull the broken segments apart.

Stellaria

Stellaria media

common chickweed [Blooms: Apr-May]

Elongated racemes or short clusters arise from snowberry's leaf axils or the tips of shoots. Each flower is about 8 mm long and 6 mm across with a dull green, hairless, tubular calyx, swollen near the base, with five shallow teeth; a bell-shaped, light pink or whitish pink corolla with five triangular lobes; five short stamens attached to the petals with tan anthers at the tip of the filament; and a light green ovary with a single style. Neither stamens nor style extend past the margin of the corolla. Long white hairs crisscross the open space inside the corolla. The fruit is a drupe (a stone fruit, like a cherry) 8-16 mm in diameter, bright white, and more or less spherical at maturity with a pair of nutlets inside.

Symphoricarpos

Symphoricarpos albus

snowberry [Blooms: Jul-Sep]

Some of coralberry's leaf axils produce dense cluster of greenish, sessile flowers. Individual flowers are 1/4" long consisting of a short green calyx with five teeth and slightly swollen basally; a stubby, tubular corolla with five bluntly-rounded lobes; five stamens with white anthers; and a pale green ovary with a hairy style. The anthers barely extend to the edge of the corolla lobes; the stigma is inset slightly deeper. The fruit is a single globoid berry containing two seeds, 1/4" long and reddish-purple when mature.

Symphoricarpos

Symphoricarpos orbiculatus

coralberry [Blooms: Aug-?]

Slender stinging nettle plants are dioecious (unisexual) with male (staminate) and female (pistillate) flowers on separate plants. Flowers occur in knobby clusters (panicles) that arise from the leaf axils. Neither pistillate nor staminate flowers have any petals. Staminate flowers have four light green, identical sepals cupping four short stamens. Pistillate flowers also have four sepals but two sepals are narrowly lance-shaped, about a millimeter long, and free, alternating with two sepals that are 1.4-1.8 mm long and cupped around the ovary; styles are absent but the single stigma is long and feathery. The fruit is a flattened, oval to egg-shaped, seed less than 1/16" long. Stinging nettles (aka, tall nettle, slender stinging nettle) have a complicated biogeographic history. According to USDA Plants (https://plants.sc.egov.usda.gov/) and ITIS.gov, the subspecies "Urtica dioica gracilis" is native, while the subspecies "Urtica dioica dioica" is an exotic that is native to Europe and Asia. Thus, you may see "stinging nettle" listed as either "native" or "exotic." Both subspecies are perennials, and both occur in Illinois, although "gracilis" is most common; most features are the same for both subspecies. Wikipedia says these subspecies are actually separate species, an opinion based on a 2014 paper in Phytotaxa (162: 61-83) that analyzed molecular characters; Kew Garden's Plants of the World Online (https://powo.science.kew.org/) and iNaturalist also accept Urtica gracilis as a valid species. I've chosen to use "Urtica gracilis" here if only to avoid further proliferation of long scientific names in this presentation.

Urtica

Urtica gracilis

slender stinging nettle [Blooms: Jul-Aug]

Wayfaring tree flowers occur in flat-topped cymes about 4" across; they are cream-colored with five petals, five stamens with white filaments and tan anthers, and a green ovary with a short (1 mm) style with a large, lobed stigma. The fruit is an oval, flattened drupe, initially red, turning black with maturity, and containing a single seed. They are not toxic but can induce vomiting it eaten when unripe. Wayfaring tree is said to be so named because it grows close to paths (and presumably other natural edges).

Viburnum

Viburnum lantana

wayfaring tree [Blooms: Apr-May]

Nannyberry flowers occur in 2-5" wide, dome-shaped panicles at the tips of young shoots. Individual flowers are 1/4" across, consisting of a light green calyx with five triangular teeth; a creamy white corolla with five oval lobes; five stamens with white filaments and yellow anthers that protrude well past the edges of the corolla lobes; and a light green or yellow pistil with a short style. The fruit is a 6-10 mm long drupe, initially green but turning dark blue-violet when ripe, containing a single seed. Nannyberry is similar to blackhaw (Viburnum prunifolium, also present in Jackson Park) — both have white flowers and blue-black fruits that are drupes — but nannyberry leaves have a long, narrow tip on their leaves in contrast to the rather blunt tips on blackhaw leaves.

Viburnum

Viburnum lentago

nannyberry [Blooms: Apr-May]

In the spring, American cranberry shrubs produce flattened panicles of flowers 2-5" across that bear two types of flowers — around the edges are five-petaled, white flowers about 1" across that are sterile (lacking both pistils and stamens), while in the center of the cluster are five-petaled, cream-colored flowers 1/4" across that are fertile (with both a pistil and five long stamens). By late summer, the flowers are replaced by bright red "cranberries" (actually drupes with a single seed) 1/4-1/2" across that prove very popular with birds (which distribute the seeds) and our local coyotes (whose scat is full of the seeds). After removing the seed, the tart flesh (high in vitamin C) can be eaten raw or cooked. In the fall, the leaves also turn red. Viburnum opulus var. americanum is said to be distinct from Viburnum trilobum (aka, highbush cranberry) by Illinois Wildflowers (www.illinoiswildflowers.info) and Minnesota Wildflowers (www.minnesotawildflowers.info), but plants.usda.gov insists that the latter is a synonym of the former. Worldfloraonline.org only adds to the confusion by insisting that the two names are BOTH junior synonyms of Viburnum opulus. ITIS.gov says that V. opulus is the correct name for the European species (now introduced to the U.S.) and Viburnum opulus var. americanum is the correct name for the American species. The easiest way to distinguish the two forms (if you care to) is to carefully inspect the nectary glands (extrafloral nectaries) on the petioles. In V. opulus americanum, the extrafloral nectaries are oval, with a concave top and a distinct rim; in Viburnum trilobum, the extrafloral nectaries are round in plan view with a convex top and no rim. Although rare in most of Illinois, guelder-rose (V. opulus americanum) is quite common around the lagoons of Jackson Park.

Viburnum

Viburnum opulus

American cranberry [Blooms: Apr-May]

Cymes of flowers arise from the leaf axils of blackhaw; the cymes are heavily branched but are sessile on the leaf axil. Individual flowers are 1/4" across with a 2 mm long calyx tube with five apical lobes that are shorter than the petals; a tubular corolla with five white, rounded lobes (the "petals"); five stamens with white filaments and yellow anthers extending outside the corolla lobes; and a small (less than 1 mm long), cream-colored pistil. The fruit is a fleshy drupe (like a plum or cherry) about 8 mm long containing a single brown nutlet that is flat on one side; the fruit becomes blue-black as it matures. The fruits are edible and popular with birds. Blackhaw is similar to nannyberry (Viburnum lentago, also found in Jackson Park) — both have white flowers and blue-black fruits that are drupes — but nannyberry leaves have a long, narrow tip on their leaves in contrast to the rather blunt tip and reddish petioles on blackhaw leaves. The stamens in blackhaw flowers are slightly shorter than those in nannyberry flowers but the difference is subtle; leaf form and petiole color are better differentiators.

Viburnum

Viburnum prunifolium

blackhaw [Blooms: May-June]