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Virginia mountain-mint flower heads are 3/4-1" across with up to 50 flowers; only a few flowers open at any one time. The flowers are hairy on the outer surfaces, white to light purple in color. Individual flowers are 1/4" across, tubular, and two-lipped; the lower lip is three-lobed with purple spots; four stamens with purple anthers emerge from the lower tube. There are two styles with deeply-notched tips that extend well beyond the edges of the lips of the corolla. The calyx that cups the flower is hairy, light green and has five triangular teeth.

Pycnanthemum

Pycnanthemum virginianum

Virginia mountain-mint [Blooms: Jul-Aug]

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]

Soapwort produces clusters of 3/4-1" flowers from the tips of terminal stems and branches. Individual flowers have a 1" long, green or reddish, sometimes hairy, cylindrical calyx; a corolla with five spreading (later reflexed), pink to white, oblong petals/lobes with a notched tip; 10 white stamens with pale yellow anthers that protrude from the throat of the flower; and a similarly protruding, divided white style. The calyx persists as an inflated seed capsule filled with 15-75 tiny dark brown, kidney-shaped seeds. Soapwort might be mistaken for a phlox, but the stamens and style in phlox are always hidden in the calyx tube, never protruding as in soapwort, and soapwort has leaves with three obvious longitudinal veins. Soapwort contains saponins in both the foliage and (especially) the seeds that make a frothy soap-like lather when boiled (and were once used as a soap substitute), but caution is recommended — the saponins are toxic. Herbivores generally avoid this plant.

Saponaria

Saponaria officinalis

soapwort [Blooms: Jun-Jul]

Mad-dog skullcap flower racemes may arise at the tips of the stems or from the axils of leaves. Each raceme is up to 6" long, containing 6-7 pairs of flowers; each flower has a short, basal leafy bract. Flowers are up to 8 mm long with a short, slender pedicel, a light green tubular calyx with two shallow lobes (the upper lobe with a dish-like projection), and a pale blue, lavender, or white, densely hairy, tubular corolla 5-8 mm long with a short, hood-like, upper lip and a slightly flared, three-lobed lower lip. Hidden inside the upper lip of the corolla are four stamens and a single bifurcated style. After fertilization, the calyx swells into a green capsule with includes the dish-like projection mentioned above, giving the capsule a unique appearance; inside is a cluster of four nutlets. The mouth of the calyx is visible as a thin slit beneath the projection.

Scutellaria

Scutellaria lateriflora

mad-dog skullcap [Blooms: Jul-Aug]

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]

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]

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]

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]

Japanese tree lilac (aka, Japanese lilac) is an exotic shrub or tree that is native to Asia; it gets 20-30 feet tall and 15-25 feet wide. It may have multiple trunks. The bark on the trunk is shiny and reddish-brown (rather like cherry trees) with horizontally elongated lenticels (air pores). The leaves are 2-5.5" long and 1-3" wide, opposite, dark green, oval with a sharp tip and a rounded base with a 1/2-1" petiole, pinnate venation, and smooth margins. The inflorescences are 6-12" high panicles dense with creamy-white flowers. Individual flowers have a 1-2 mm long calyx; a 3-5 mm long cream-colored corolla with five stubby lobes (petals) and a four-lobed apex; five white stamens with yellow anthers widely spreading radially; and a single long white style bearing a club-like stigma. The fruits are 3/4" long dry capsules, initially green but turning reddish-brown or yellow with maturity. The capsule splits to release the two winged seeds.

Syringa

Syringa reticulata

Japanese tree lilac [Blooms: Jun-Jul]

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]

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]

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-?]

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]