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Spectacular and unmistakable red and yellow, columbine's bell-like flowers hang aperture down from an arching flower stalk; the four elongate, parallel spurs point up while the stamens and style emerge from the bottom of the flower. This is the only columbine native to Illinois.

Aquilegia

Aquilegia canadensis

red columbine [Blooms: Apr-Jun]

An ornate pink flower with multiple levels of petals above a central core of projecting yellow stamens. This variant of Aquilegia vulgaris ("stellata" commercially called 'Nora Barlow') is a genetic variant that produces multiple stacked flowers (like the difference between a wild rose and commercial roses).

Aquilegia

Aquilegia vulgaris

common columbine [Blooms:May-Jun]

Japanese angelica tree may be mistaken for the (native) devil's walking stick, Aralia spinosa. However, the Japanese angelica tree (A. elata) has shorter (although quite substantial) compound leaves, sessile leaflets directly attached to the petiolule, a smaller inflorescence (about 2' tall rather than over 3'), and shorter, less intimidating spines on the trunk. Leaf venation (best viewed from the underside) is the best way to differentiate the two. In devil's walking stick, the pinnate leaf vein tips curve to form a sub-marginal vein parallel to the leaf margin. In the Japanese angelica tree, the leaf veins extend all the way to the margins of the leaf.

Aralia

Aralia elata

Japanese angelica tree [Blooms: Jul/Aug–?]

Spikenard is superficially similar to devil's walking stick (Aralia spinosa) but lacks the spiny leaves and stem of the latter. Both produce a terminal inflorescence of flowers (20+ ft. up). Unlike devil's walking stick, the flowers of spikenard are perfect; i.e., they have both male (stamens) and female (a stigma) parts. In this photo, both flower buds and flowers with prominent stamens are apparent.

Aralia

Aralia racemosa

spikenard [Blooms: Jul-Aug]

A small, somewhat shrubby tree up to 25' tall, although half that height is more common in Jackson Park (which is near the northern limit of its range). Devil's walking stick produces a terminal inflorescence of flowers (20+ ft. up). Flowers are small (1/4" long), white and are produced in umbels at the top of the tree. Devil's walking stick has flowers that are either male (bearing stamens) or female (bearing styles). The male flowers of devil's walking stick have prominent stamens and five white, triangular petals; the female flowers (shown here) look like rounded green buds with five stout styles emerging from the distal end.

Aralia

Aralia spinosa

devil's walking stick [Blooms: Aug-Sep]

Burdock has thistle-like, composite flowers with lavender to purple (rarely, white) disc florets but no ray florets; the surrounding bracts are green and strongly hooked.

Arctium

Arctium minus

burdock [Blooms: Jul-Oct]

Bearberry produces small clusters of 2-15 flowers from the tips of the previous year's twigs. Individual flowers are urn- or bell-shaped with a constricted opening ringed by five short lobes, 1/2" long and wide; they have a five-lobed flattened calyx, a white or pink corolla, 10 stamens, and a single style none of which protrude outside the corolla. The flower pedicels are about 1/4" long, red and have a narrow bract at their base. The fruit is a spherical drupe 1/4-1/2" across, initially whitish green but red at maturity.

Arctostaphylos

Arctostaphylos uva-ursi

bearberry [Blooms: April]

Two thyme-leaved sandwort flowers, with leaves clearly visible on the stem on the left of the image. Easily overlooked as just another chickweed, thyme-leafed sandwort's petals are not deeply notched like chickweeds. The stems are 6-10" tall, erect or sprawling, dark purple, and covered with fine hairs. Tiny (4 mm) white flowers on 1/4" pedicels with backward-pointing hairs; flowers have five pointed, white, oblong petals; five hairy green sepals longer than the petals; ten white stamens with magenta anthers; a green central ovary; and three white styles. An exotic from Europe that prefers disturbed areas with minimal other vegetation.

Arenaria

Arenaria serpyllifolia

thyme-leaved sandwort [Blooms: Apr-Jun]

Jack-in-the-pulpit is iconic and unmistakable wildflower. Plants are 1-2' tall; they don't flower until at least 3 years old. Each plant has a single upright stalk (a.k.a., the peduncle) that produces the inflorescence; the stalk develops directly from an underground storage organ, the corm. The inflorescences are light green to reddish green, often with reddish-brown stripes. The outermost spathe wraps loosely around the robust, cylindrical spadix; the top of the spathe bends 90° to form a hood (the "pulpit") over the spadix ("Jack"). The top half of the spadix produces volatile compounds that attract small insects, especially fungus gnats; the insects carry the pollen between plants. The bottom half of the spadix bears highly reduced florets. Both male and female florets lack petals; male florets consist of four stamens while female florets consist only of a stigma attached directly to the top of the ovary. Each plant typically has EITHER male or female florets located on the bottom half of the spadix; a single plant usually produces only one sex of florets in a given season, but plants switch between male and female multiple times during their ~20 year lifespan (they are "sequential hermaphrodites").

Arisaema

Arisaema triphyllum

Jack-in-the-pulpit [Blooms: Apr-Jun]

Flowerheads of pale Indian plantain. These plants can be to 9' tall and commonly reach 6+ feet; the stem is pale green to purple with a whitish cast. The flat-topped apical flowerhead is shaped like an inverted pyramid made up of small (1/8x3/8") tubular, cream-colored flowers with five disc florets surrounded by five bracts.

Arnoglossum

Arnoglossum atriplicifolium

pale Indian-plantain [Blooms: Jun-Aug]

Prairie Indian plantain flowerheads are tubular, 3/16" x 3/8", greenish white to reddish white, with five disc florets surrounded by five bracts with white keels (which distinguishes them from pale Indian plantain flowerheads).

Arnoglossum

Arnoglossum plantagineum

prairie Indian-plantain [Blooms: Jun-Jul]

Red chokeberry is a 6-12" tall shrub with multiple stems. Flowers are white with red tinge on the tips of the 5 petals; each flower is ~1" in diameter.

Aronia

Aronia arbutifolia

red chokeberry [Blooms: Apr-May]

Black chokeberry flowers occur in clusters of 7-12 near the margins of the shrub. Each flower is ~1/2" across with a reddish-green calyx with 5 short triangular lobes, 5 white, spoon-shaped, non-overlapping petals with rounded tips and a narrow base, 16-20 stamens with pink to rose-colored anthers, and 5 pale green styles, fused at their bases. The red glands on the upper leaf midvein and pink to rose-colored stamens are diagnostic of black chokeberry.

Aronia

Aronia melanocarpa

black chokeberry [Blooms: May-?]

Beach wormwood is an unusual plant 2-4' tall with characteristic, deeply dissected leaves. The flowerheads are 2-4 mm long and wide; each is composed of 5-20 outer disk florets that bear only stamens and 8-30 inner disc florets that possess both pistils and stamens. There are no ray florets.

Artemisia

Artemisia campestris

beach wormwood [Blooms: Aug-Sep]

Mugwort's Inflorescence consists of leafy spikes covered with inconspicuous flowerheads, initially whitish-green, later yellowish- or purplish-green; the flowerheads are egg-shaped, very small (1/8" across) and bear only disc florets (ray florets absent).

Artemisia

Artemisia vulgaris

mugwort [Blooms: Jul-Oct]

Wild ginger's flowers are ~1-2" across, reddish-brown on the outside, cream colored on the inside, that develop from an axis at the junction of the two leaves (one flower per plant). The flower calyx consists of three triangular sepals with the long tips curled backwards; the tubular base of the calyx is divided into three pairs of chambers (six total) which contain the ovaries, twelve stamens, and six reddish-brown styles. Because the flowers are brown and occur right at ground level, they are easy to overlook and usually can only be seen by parting the leaves.

Asarum

Asarum canadense

wild ginger [Blooms: Apr/May-?]

Prairie milkweed produces one and a half to two inch balls of 30-100 greenish-white flowers in the axils of a few of the mid-stem and upper leaves; the flowers are supported on 1/2"-3/4" pedicels. Each flower is about 1/8" across and 1/4" long; the flowers are a variation on the typical (complex) milkweed morphology with 5 sepals, a 5-lobed corolla with 5 petals (often with purple blotches at their tips) that are reflected backwards to cover the top of the pedicel, 5 hoods without horns, and a short central column that rises above the hoods; there is a distinct gap between the bases of the petals and the crown. Seedpods are 4-5" long with a fat base (attached to the pedicel) tapering rapidly to a narrow tip. Prairie milkweed can be confused with whorled milkweed (Asclepias verticillata) — both occur in Jackson Park — but whorled milkweed has even narrower (grass-like) leaves than prairie milkweed, is a shorter plant, and has pure white flower that do bear horns.

Asclepias

Asclepias hirtella

prairie milkweed [Blooms: Jun-Aug]

The flowerheads of swamp milkweed are erect, ~3" across, with 10-40 flowers; flowers are 1/4" across and typical milkweed morphology with pink petals and whitish hoods, but color can vary from pink to magenta; the central column is cream-colored and visible below the base of the hoods. The petals are reflected backwards but are not tightly pressed against the stem; the horns arch up and over the central column and taper to a sharp point.

Asclepias

Asclepias incarnata

swamp milkweed [Blooms: Jul-Aug]