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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]

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]

White blue-eyed grass is a native perennial, 6-12" tall with a tuft of basal leaves and flowering stalks that are grass-like (if you squint). The basal leaves are green, 1/8" across, and strap-like; they are shorter than the flowering stalks. The flowering stalks are weakly winged and have a pair of sessile spathes (bracts sheltering the inflorescence) at their tips. The spathes consist of a pair of 1" long reddish or light brownish green bracts backed by a 3" long leafy bract; an umbel of up to six flowers arises between the bracts but only one or two flowers are in bloom at any given time. Each flower is only about 1/2" across and is supported by a 1/2" long pedicel. The flower consists of six white or pale blue tepals with a yellow patch at their bases and narrow, dagger-like tips; a column of yellow or orange-yellow stamens fused along their length almost to the anthers; and a globoid, green ovary covered with fine hairs and sporting a style with three slender lobes. Fertilized flowers produce a ridged, globoid seed capsule, initially green but turning tan to brown as it matures.

Sisyrinchium

Sisyrinchium albidum

white blue-eyed grass [Blooms: May-?]

Water parsnip's upper stems end in 2-5" wide, flat-topped umbels of flowers with numerous (10-20) umbellets, each with 20-35 tiny (1/8" wide) flowers. At the base of the umbel are 6-10 narrow bracts that are curved down towards the stem. Each flower has a 3-5 mm long stalk; a short, light green calyx; five white, heart-shaped petals with incurved tips; five stamens that extend well outside the flower; and an ovary with two diverging styles. The fruits are 3 mm long, slightly laterally compressed, oblong, with strong ribbing; each fruit contains exactly two seeds.

Sium

Sium suave

water parsnip [Blooms: Jul-Aug]

Horsenettle's upper stems end in small clusters of 3/4" wide white or light violet flowers with wavy petal margins and hairy pedicels; clusters may also arise from leaf axils. Each flower has a green, hairy calyx with five lobes that taper gradually to sharp tips (typically slightly reflexed); five triangular petals that are fused at their bases; and five yellow, banana-shaped anthers 6-9 mm long surrounding a long, slim, light green style with a darker green, globular terminal stigma. After fertilization, the ovary expands into mature berries about 1/2" in diameter, initially green-striped, that look like yellow cherry tomatoes when mature; they are half enclosed in a papery derivative of the calyx.

Solanum

Solanum carolinense

horsenettle [Blooms: Jun-Aug]

Black nightshade produces solitary umbels 3/4" long usually, from the axils of middle and upper leaves; the flower pedicels are about 3/8" long. Flowers are 1/4-3/8" across consisting of five sepals partially fused at the base of the flower; five white petals, green at their base, sometimes with purple highlights on the outside of the petal, and usually curved backwards; five anthers and their thick filaments appressed to form a tight, bright yellow cylinder with a yellowish-green stem; and a slender style running up the center of the appressed anthers to just emerge from the tip as a green stigma. The fruit is a 1/4-3/8" tomato-like berry, initially green; mature berries are black. The foliage and unripe fruit contain the alkaloid solanum and are toxic.

Solanum

Solanum ptychanthum

black nightshade [Blooms: Jul-Sep]

Upland white goldenrod stems end in a flat-topped panicle 6" across of flowerheads; colonies can present a visually continuous surface of flowers. The flowerheads are 3/4-1" across on 1" stems; each flowerhead has 10-25 white, pistillate ray florets (no stamens) and 30-36 yellowish, perfect disc florets (with both pistils and stamens). The petal-like rays are bright white and spreading, sometimes with notched tips; they look very much like a generic aster flowerhead. The disk florets are dull white and tubular; the five stamens in each disk floret are conjoined and yellow, giving a yellowish cast to the disk. Behind the flowerhead are 4-5 series of hairless bracts (phyllaries), light green at their base, darker green at the tips, each phyllary with a prominent light green mid-vein; the phyllaries are 4 mm long in total. Upland white goldenrod is uncommon in most of northern Illinois except in the sandy soils near Lake Michigan. ITIS and the Flora of North America accept Solidago ptarmicoides as a valid species name; the USDA Plants Database and NatureServe Explorer consider S. ptarmicoides as a junior synonym of Oligoneuron album (as does illinoiswildflowers.info).

Solidago

Solidago ptarmicoides

upland white goldenrod [Blooms: Aug-Sep]

The central stem of giant bur-reed produces an inflorescence at its tip with 1-6 female flowers in the lower parts of each branch of the inflorescence and up to 20 male flowers in the upper parts. (Male and female flowers are separate and distinct.) Male (staminate) flowerheads look like a fireworks-burst of white filaments and yellow-brown anthers; individual florets are densely packed, each with five stamens with white filaments and a yellow to brown anther. The female flowerheads are greenish and "prickly" with prominent green cones (the female florets) covering the surface; each pistillate floret has a basal green ovary covered with scale-like tepals with dark tips and an apical white style bearing two white stigmas. Giant bur-reed is wind pollinated. In fruiting flowerheads, the stigmas turn dark and wither but do not drop off; the florets elongate and widen, turning brown as the fruits on the seedhead ripen. The fruit is a brown seed 5-10 mm long and nearly as wide, shaped like an inverted pyramid that abruptly narrows to a 2-4 mm long apical beak (the style remnant). Giant bur-reed is superficially sedge-like but instead is more closely related to cattails. Giant bur-reed prefers wet conditions (up to a foot of water) with minimal waves and gentle currents.

Symphytum

Sparganium eurycarpum

giant bur-reed [Blooms: May-Jul]

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]

White meadowsweet's branches end in 2-6" long, oblong or pyramidal (1-4 times longer than wide) panicles of densely packed flowers that open from the top down. The flowers are about 1/4" across and are very similar to Eastern Meadowsweet (Spiraea latifolia) except for color (white rather than pink, although often pink as buds). Individual flowers consist of five triangular, light-green sepals; five white petals narrowest at their base, longer than the sepals; numerous (15-50) long, white stamens with white or pink anthers; and five light green or white pistils. The long stamens on the flowers give the flowerhead a fuzzy outline. The fruit is a cluster of 4-6 follicles, each containing one seed. When ripe, the top of the follicle splits, allowing the seed to fall out when the stem is shaken. Surrounding the pistils is a ring of pink, orange, or yellow tissue that marks the location of the nectaries. White meadowsweet prefers wet areas along the lagoons in Jackson Park.

Spiraea

Spiraea alba

white meadowsweet [Blooms: Jul-Sep]

Great Plains ladies'-tresses flowers are arranged in three rows spiraling up around the stem. The petals and sepals are both white with a tinge of yellow on the lower lip (lower petal). The two petals are top and bottom of the bloom, with the lower, ruffled petal extending out and down; the two sepals are narrower than the petals and flank the side of the bloom, sometimes arching higher than the petals. Typically, there is a single stamen; the style is fused to the surface of the lower petal deep in the flower. The base of the flower is nestled between oval green bracts which cup the ovary and taper to a sharp point above the flower. Great Plains ladies'-tresses are probably pollinated by bumblebees, but information is sparse. If you get down on your hands and knees (or, better, lie down beside the plant) and put your nose up against the blooms, it is really true that they smell like vanilla(!). A closely related species, nodding ladies'-tresses (Spiranthes cernua) was once considered to be the same species as Great Plains ladies tresses, but the former still has its basal leaves on blooming and no scent while the latter never has the basal leaves when blooming and the flowers smell like vanilla.

Spiranthes

Spiranthes magnicamporum

Great Plains ladies'-tresses [Blooms: Sep]

Bladdernut produces white, drooping, bell-shaped flowers in clusters of 5-12 from the axils of the leaves. Each flower is pendant on a long stalk, bell-shaped, about 8 mm long and about 6 mm wide. Flowers have five greenish-white sepals overlapping much of the petals, five bright white petals (visible through the gaps between the sepals) that flare at their tips, five stamens with white filaments and deep yellow-orange anthers, and a greenish-white style with a three-lobed stigma extending beyond the mouth of the bell. The flower stalks (pedicels) are about 1.5-2 times the length of the flower. The fruit is a greenish-white to brown, papery pod (like a "Chinese lantern") that is about 3" long and 2" across with three lobes/chambers, pointed on their distal ends; each chamber contains up to four 1/4" seeds. Both flowers and fruits are distinctive and easily recognizable.

Staphylea

Staphylea trifolia

bladdernut [Blooms: Apr-May]

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]

Trailing wild-bean is a native annual, a sprawling or climbing vine 3-9 feet long found in sandy habitats. The stems are slender, round in section, range from light green to dull reddish, and are quite hairy; they produce occasional branches and can twine around neighboring plants. Leaves are alternate, trifoliate compound, with broadly oval to teardrop shaped leaflets 1-2" long and 1/2-1.25" across, widest at the base with a pointed tip. The terminal leaflet may be slightly larger and has a short stalk (petiolule); the lateral leaflets are sessile. Sometimes the bases of the leaflets have a shallow lobe on each side of the midline. The compound leaf has a 1-2" long, slightly fuzzy petiole. Some leaf axils produce 3-6" long flower stalks (peduncles) with 3-10 nearly stalkless flower buds at the tip, only a few of which are open at any one time. The flowers are 1/3-1/2" across, light pink to creamy pink, pea-like with five petals, but the keel is sharply curled upward such that it almost touches the banner (the vertical petal). The fruit is a bean-like seedpod, 2-3.5" long, sparsely covered with short hairs, initially green but turning dark brown as it matures; the seeds are oblong, black, and are also covered with short hairs.

Strophostyles

Strophostyles helvola

trailing wild-bean [Blooms: Aug-Sep]

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]

Each heath aster flowerhead is 1/3-1/2" across with 8-20 ray florets (usually 12) and 6-12 disk florets. The ray florets are sterile; the disk florets are perfect and fertile. The phyllaries occur in 3-4 series on the back of the flowerhead; they are blunt-tipped, often recurved away from the flowerhead, with a distinct apical spine. Also note the spines at the tips of the numerous needle-like bracts on the flower stems. (Note: hairy aster (S. pilosum) also has such apical spines but has larger flowers, rolled, needle-like phyllaries with a smaller spine, and spreading hairs on the stems.)

Symphyotrichum

Symphyotrichum ericoides

heath aster [Blooms: Sep – Nov]

Panicled aster's central stem gives rise to an 8" long panicle (4" wide) of flowerheads; panicles may also arise form lateral stems and the axils of upper leaves. The panicle branches tend to be hairier and more often grooved than the stems; there are bracts (1.5" long, 8 mm wide) at the base of the panicle branches and the base of the flowerhead stalks. Individual flowerheads are 1/2-3/4" across with 1.5" long flower stalks (peduncles). Flowerheads have 20-40 white (less often blue or violet), pistillate (no stamens) ray florets, and an equal number of perfect (pistils and stamens) disc florets that are initially yellow, turning red orange with age. Phyllaries (bracts) cover the back of the flowerhead in 3-6 overlapping layers; the phyllaries are narrow, green with paler bases, appressed or slightly spreading, with the outer layer shorter than the inner. The fruit is a 1.5-2 mm long gray seed with a tuft of dull white or yellowish hairs. It's easy to confuse panicled aster with other asters that have small, white flowerheads. Look for: (1) leaves with wedge-shaped (not rounded or heart-shaped) bases, (2) mature leaves hairless on both sides, (3) stems with lines of white hairs, and (4) flowerheads with at least 20 ray florets. (Count the "petals.")

Symphyotrichum

Symphyotrichum lanceolatum

panicled aster [Blooms: Aug – Oct]

Panicles of flowerheads up to 10" long and 6" across arise from the upper stems (and some side stems) of calico asters. Individual flowerheads are about 1/3" (8 mm) across, typically consisting of 8-15 white ray florets and 8-16 cream or light-yellow disc florets turning brown or reddish purple with age. The flowerheads sit on a 1/3" long, hairy flower stalk (peduncle) with a few leaf-like bracts along the peduncle. The base of the flowerhead is covered by phyllaries (bracts) in 3-4 overlapping layers; the phyllaries are sparsely hairy, appressed or slightly spreading, with a darker green lance- or diamond-shaped tip. The fruits are fuzzy dry seeds with a tuft of white hairs. Calico asters are distinguished from other small, white asters by: (1) very small flowerhead (<1/2"), (2) relatively few (9-16) ray florets/petals, (3) creamy white or pale (not bright) yellow disk florets, (4) lance-elliptic leaves with hairs only on the midvein, (5) stems with lines of soft, white hairs. Other asters (e.g., panicled aster) will have one or more of these characters, but not the full suite.

Symphyotrichum

Symphyotrichum lateriflorum

calico aster [Blooms: Sep – ?]