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Field pennycress's central stem and the upper side stems produce racemes of flowers at their tips. The flowers bloom at the tip of the raceme, which continues to elongate to 3-8" long and to produce new buds; the prominent, disk-shaped fruits develop lower on the raceme. Individual flowers are about 1/8-1/4" across on a 1/2" pedicel; there are four green sepals with whitish edges, four white, oval petals, six yellowish-green stamens (three on each side of the flattened ovary), and a single short style. The fruit is a 1/2" wide flattened, winged disc with a distinct U-shaped notch at the apex; the fruits are borne on the flower pedicels, which spread perpendicular to the stem. Each seedpod has two compartments, each compartment containing several dark brown seeds. Other mustards have long, cylindrical seedpods; the nearly-circular seedpod of field pennycress is unique among Jackson Park mustards. Young field pennycress plants are edible but become very bitter at flowering. Cows that feed on field pennycress produce "tainted" milk that tastes like garlic.

Thlaspi

Thlaspi arvense

field pennycress [Blooms: Apr-Jun]

Erect hedge-parsley's main stem and side stems give rise to umbels 1.5-2" across of 10-20 umbellets of flowers. Each flower is about 1/8" across consisting of five white petals (often markedly unequal in size), and a creamy white center surrounded by five pink to white stamens. The fruit is an 1/8" long oval covered in hooked hairs to aid in bur-like dispersal; it contains two seeds. (The fruit of common hedge-parsley (Torilis arvensis) has straight or only slightly curved hairs, not hooked, but the hairs are barbed.)

Torilis

Torilis japonica

erect hedge-parsley [Blooms: Jun-Jul]

Alsike clover is an exotic perennial native to Europe. Despite the scientific name ("hybridus"), it is not a hybrid. (Linnaeus thought it was a hybrid of red and white clover. It isn't.) The plant is 6-24" tall, with occasional branches along the stems. One- to three-inch-long flower stalks arising from the leaf axils terminate in a flowerhead 1/2-3/4" across; florets tend to be white on the top of the flowerhead and reddish-purple to pink on the bottom, but may all be reddish. Individual florets are 1/4" long with five petals in a pea-like bloom. They have a sharply pointed standard (the major vertical petal, perpendicular to the keel), two petals that make up the keel, and two lateral petals that flank the keel. Ten stamens and a single pistil are hidden inside the keel. Unlike red clover (T. pratense) and white clover (T. repens), there are no pale chevron-shaped markings on the leaflets.

Trifolium

Trifolium hybridum

alsike clover [Blooms: May-Jul]

White clover's hairless, leafless flower stalks are up to 3" long. They emerge directly from the horizontal stems and grow perpendicular to the ground, producing a single globular 3/4" wide flowerhead at their tips. The flowerheads are all white, consisting of 20-50 pea-like florets. The florets are tubular, consisting of a green calyx with five long, narrow teeth, and five white or pinkish-white petals (a standard, two petals making the keel, and a pair of lateral petals flanking the keel). White clover is similar to alsike clover (T. hybridum), but that species usually has some pink in the flowerheads and never has white chevrons on the leaflets.

Trifolium

Trifolium repens

white clover [Blooms: May-Jun]

Large-flowered trillium's single flower sits on a 1-3" long flower stalk; the flower is 3-4" across and leans to one side (but doesn't droop). The flower consists of three green, lance-shaped sepals with rounded bases, three white (pinkish in older flowers) petals with wavy edges, six stamens with golden yellow anthers, a central white ovary, and three styles fused basally but with separated, dull-yellow stigmas. The fruit is a six-angled, globose capsule, about 1/2" long, that is initially green but darkens as it matures; it splits open to release the seeds. The seeds carry an attached oily, fleshy food reward (an elaiosome) and are dispersed by ants which inadvertently deposit the seeds in their nests to take advantage of the reward. Large-flowered trillium prefers shady environments like woodlands and is slow to mature — it can take several years for a sprout to produce flowers.

Trillium

Trillium grandiflorum

large-flowered trillium [Blooms: Apr-May]

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 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.

Urtica

Urtica dioica

stinging nettle [Blooms: Jul-Aug]

Clusters of lowbush blueberry's flowers develop on the previous year's twigs. The flowers are about 1/4" long, urn- or bell-shaped, nodding, white, and waxy. The flowers contain a short, green calyx with five teeth; a short, tubular corolla that is pinkish white or white with five triangular, recurved lobes around its margin; ten stamens with reddish brown anthers recessed behind the margin of the corolla and clustered around the style; and a single style whose stigma extends right to the margin of the corolla. Fertilized flowers are replaced by approximately 8 mm diameter berries, initially green but turning dark blue with a whitish bloom as they mature. (I.e., they look — and taste — like blueberries.)

Vaccinium

Vaccinium angustifolium

lowbush blueberry [Blooms: May]

White vervain produces numerous 6" long, widely spaced flower spikes, each covered by tiny (1/8" wide) white flowers sparsely distributed along the length of the flower spike. Individual flowers consist of a hairy, tubular green calyx with five lance-like teeth and a curved, tubular corolla that abruptly flares into five short, rounded, brilliant-white lobes ("petals"). The throat of the flower is "bearded" (occluded by white filaments extending to the middle of the opening), hiding four stamens with greenish anthers, a green style, and a two-lobed stigma. The upper (more apical) two lobes of the corolla are slightly smaller than the other three (like prostrate vervain) and the tip of the lowermost lobe of the corolla is notched (like hoary vervain), but you're not likely to confuse white vervain with any other Verbena. The fruit is four oblong nutlets nestled in the remnants of the calyx.

Verbena

Verbena urticifolia

white vervain [Blooms: Jun-Sep]

Wayside speedwell's flowers are 1/4" across with a green, hairy calyx with four triangular lobes as long as the petals, projecting between them in the spaces between petals; a short corolla with four spreading lobes, three the same size (one on either side, blue to bluish-white with dark blue lines, and the third dark blue with blue-violet lines) and one about half as wide, pale blue or white with light blue lines. The blue lines function as nectar guides. The base of all four lobes is bright white, but the center of the flower is greenish. There are two white stamens with white anthers (backed by a dark blue "U" shape) and a single white pistil emerging from the throat of the corolla. The fruits are heart-shaped capsules with two chambers covered with glandular hairs, each containing 8-12 seeds. The flowers and leaves of wayside speedwell are similar to those of bird's-eye speedwell (Veronica persica), but the calyx lobes of bird's-eye speedwell do not project beyond the petals. There are 16 species of the genus Veronica reported from Illinois. I have only seen three (Veronica arvensis, Veronica polita, and Veronica serpyllifolia) in Jackson Park but, given their minute size and inconspicuousness, it seems likely that more remain to be found.

Veronica

Veronica polita

wayside speedwell [Blooms: Apr-Jun]

Thyme-leafed speedwell's upper stems host clusters (racemes) of flowers 2-7" long; flowers may either be opposite or alternate along the stem. Each flower is 1/8-1/4" across with a short (1/4"), slender petiole; at the base of the petiole is an oblong, hairless, leafy bract also about 1/4" long with smooth margins. (Thus, the flowers effectively arise from leaf axils.) Individual flowers consist of a green calyx with four triangular lobes shorter than the petals; a short corolla with four oval petal-like, lobes (the lowest one smaller than the other three); two stamens with purple or white anthers; and a green ovary with a single style. The lobes (petals) are white or pale blue, usually with dark blue lines radiating from the flower's center on the upper three lobes. The fruit is a laterally flattened, heart-shaped capsule 1/4" across with two chambers and a fringe of glandular hairs. When mature, the chambers split open, releasing 50-72 tiny seeds. There are 16 species of the genus Veronica reported from Illinois. I have only seen three (Veronica arvensis, Veronica polita, and Veronica serpyllifolia) in Jackson Park but, given their minute size and inconspicuousness, it seems likely that more remain to be found.

Veronica

Veronica serpyllifolia

thyme-leafed speedwell [Blooms: Apr-?]

At the top of the Culver's root plant are floral spikes (racemes) up to 10" long covered with small (1/4" long) white, tubular flowers. Individual flowers consist of a short (3 mm long), green calyx with five deep lobes (the lower two lobes longer than the upper three); a tubular corolla with four lobes (the lower two longer than the upper two); two stamens with yellow or reddish brown anthers; and a single style with a tiny stigma. The stamens and stigma protrude well beyond the lip of the flower. The flowers bloom from the base of the floral spike successively towards the tip. The fruit is a 2.5-4.5 mm long ovoid capsule with four apical teeth. The capsules contain 10-30 half millimeter long, ovoid seeds. Culver's root is very popular with a wide diversity of bees.

Veronicastrum

Veronicastrum virginicum

Culver's root [Blooms: Jun-Aug]

Korean spice viburnum's inflorescences are 2.5" diameter umbels of flowers on the tips of new twigs. The flowers are aromatic; the scent is described by the Chicago Botanic Garden as "sweet, rich, and complex with a hint of cloves." The flowers are fragrant for only about two weeks. Individual flowers consist of a tiny (1 mm long), reddish green calyx with five lobes; 8-10 mm long tubular, pale pink to white corollas with five abruptly spreading lobes; five stamens with yellow anthers just inside the throat; and a short (1 mm long), stout style with a knob-like stigma. The corolla is about 1/2" across. Korean spice viburnum flowers are superficially similar to butterfly-bush (Buddleja davidii), which also occurs in Jackson Park, but the latter has a spike-like inflorescence rather than an umbel.

Viburnum

Viburnum carlesii

Korean spice viburnum [Blooms: Apr]

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]

Many of the upper shoots of downy arrowwood end in 1.5-3" wide, dome-shaped panicles of flowers with slightly fuzzy, light green branches. Individual flowers are 1/4" across with a short, light green calyx with five short, broad teeth; a white tubular corolla with five rounded, spreading lobes; five stamens with white filaments and tan anthers that extend outside the corolla; and a single white style. The flowers have an unpleasant odor described by various sources as "rotting flesh." The fruit is a small (1/4-1/2") drupe (a stone fruit like cherries or a plum) 8 mm long and dark blue-violet to black at maturity. Downy arrowwood can be distinguished from other Viburnum spp. by its (1) its small size (less than six feet tall), (2) the relatively few teeth along the leaf margins (5-10 per side), (3) the short (about 1/4") leaf petioles, (4) the small, narrow stipules at the petiole bases, and (5) its flowers' unpleasant odor. The common name derives from the fact that the straight stems of the various arrowwoods was preferred by indigenous Americans for arrow shafts.

Viburnum

Viburnum rafinesquianum

downy arrowwood [Blooms: Aug–Sep]

Wild pansy's flower stalks are long, hairless, and bend like a shepherd's crook just below the base of the flower so the flower axis is approximately horizontal. Individual flowers have five 7-15 mm long, lance-shaped sepals that are longer than the petals and are sharply pointed at their tips; a 4-12 mm long corolla with five white or pale cream-colored petals, a yellow throat with a few dark purple lines, the lateral petals bearded on their upper surface, and a 1-1.5 mm long spur; two stamens not visible externally; and a single style enlarged into a hollow, globose stigma. The fruit is a spherical or ellipsoidal three-valved capsule, 5-10 mm long containing 6-75, 1.5 mm long, brown seeds.

Viola

Viola arvensis

wild pansy [Blooms: Jun-?]