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Common sowthistle flowerheads are less than 3/4" in diameter and look very dandelion-like; they open in the morning and close by noon. Each flowerhead consists of numerous (80-250) yellow ray florets; disc florets are absent.

Sonchus

Sonchus oleraceus

prickly sowthistle [Blooms: Jun-Oct]

The leafy stems of Drummond's aster end in a panicle 1/2-2 feet long and half as wide bearing white flowerheads with yellow or maroon centers. Individual flowerheads are 1/2-3/4" across; they have 10-15 ray florets and 13-15 disk florets. The ray florets have bright blue, purple, or white tubular corollas and white rays (petals); the disk florets have cream to yellow tubular corollas, turning deep purple or reddish purple with age. Both disk florets and ray florets are perfect with bright yellow anthers on the stamens and white, bifurcated styles, but the ray florets are sterile. The base of the flowerhead is covered with 4-5 series of overlapping, light green phyllaries (bracts). Each phyllary is 4-6 mm long, light green, with a diamond-shaped patch of dark green near their tip. The fruit is a dry seed with a tuft of attached brown to white hairs. Note that the leaf petioles are winged and the leaves are broad and toothed. The upper surface of the leaf is rough (unlike Short's aster, the most common species in Jackson Park that you might confuse with Drummond's aster). The even pubescence (down-like hairs) on the underside of the leaves and along the stems distinguishes Drummonds aster from the other look-alike aster in Jackson Park, white arrowleaf aster (Symphyotrichum urophyllum). The phyllary pigmentation is also distinctive.

Symphyotrichum

Symphyotrichum drummondii

Drummond's aster [Blooms: 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]

Smooth blue aster's central stem produces a one-half to one foot long (and half as wide) panicle of flowerheads with stiff, ascending branches covered with small, leafy bracts. Smaller panicles may arise from some lateral upper stems and the axils of the upper leaves. Individual flowerheads are 0.5-1" wide, consisting of 15-30 light lavender or light blue-violet ray florets and 19-33 disk florets that are initially a whitish yellow but change to purplish red over time. The phyllaries that cover the back of the flowerhead are arranged in 4-6 overlapping series and have a diamond-shaped, green tip, often with a spot of red at the very tip. The fruit is a brown, dry seed, flattened, narrowly cone-shaped with 4-5 longitudinal ribs, 2-4 mm long with a tuft of brown hair. The most useful character to distinguish smooth blue aster from other asters is the lack of hairs on its stems and leaves; the uniformly clasping leaves (no petioles) is another useful character. For example, the superficially similar skyblue aster (Symphyotrichum oolentangiense) has lower and middle leaves with distinct petioles and none of its leaves actually clasp the stem.

Symphyotrichum

Symphyotrichum laeve

smooth blue aster [Blooms: Aug – Sep]

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 – ?]

Clusters of flowerheads occur at the tips of the upper stems of New England asters. Individual flowerheads are large (1.5" across) with 50-75 (!) purple, lavender, or pink ray florets; the 50-110 disk florets are yellow or gold, turning reddish purple with age. A healthy New England aster with two or three dozen flowerheads is an impressive sight indeed. Phyllaries surround the back of the flowerhead in 3-5 layers. They are green or purple-tinged, very narrow but robust, widely spreading or reflexed, with the outermost layer of phyllaries covered with short glandular hairs. The fruit is a longitudinally ribbed, quite hairy, dry seed with a tuft of long, light brown hairs. The large, showy flowerheads with very large numbers of ray florets (petals) can't be confused with any other aster in Jackson Park.

Symphyotrichum

Symphyotrichum novae-angliae

New England aster [Blooms: Aug – Nov]

Skyblue aster's central stem terminates in a 6-18" long panicle of flowerheads; the panicle is twice as long as wide. The panicle has a central stalk (rachis), several primary branches and numerous secondary (off the primary) and tertiary (off the secondary) branches that end in flowerheads. The branches have scale-like, 3/4" long leafy bracts spaced along their lengths. Individual flowerheads are 1/2-3/4" across with 10-25 lavender or pale blue ray florets and 20-25 disk florets. The disk florets are initially yellow, turning reddish-purple with age; they seem to me to be unusually large for an aster. The phyllaries (bracts) surrounding the base of the flowerhead are small (2 mm) and tightly appressed, each with a diamond-shaped green tip and often with a spot of blue-purple at the very tip. The fruits are bullet-shaped, 1.5-2mm long dry seeds, purplish brown, with a tuft of hairs. Skyblue aster is similar to smooth blue aster (S. laeve), but that species has sessile leaves; sky blue aster has petioles on the lower and middle leaves, only the upper leaves are sessile. Skyblue aster is also similar to Short's aster (Symphyotrichum shortii), but the latter has upper leaves with a heart-shaped base rather than smoothly tapering to a sessile attachment as in skyblue aster. Generally, skyblue aster is most easily identified by the long, narrow, arrowhead-shaped lower leaves that feel like fine sandpaper on both surfaces.

Symphyotrichum

Symphyotrichum oolentangiense

skyblue aster [Blooms: Sep – Oct]

The upper stems of hairy aster give rise to 2 foot long, 1.25 foot wide panicles with a central rachis that produces spreading or ascending primary branches and smaller secondary branches that bear the flowerheads. Each flowerhead is 1/2-3/4" across with 15-35 white ray florets and 20-40 yellow disk florets that turn reddish purple or brown with age. The bracts (phyllaries) that surround the base of the flowerhead are present in 4-5 layers; they are 3 mm long and light green with a long, darker green tip. The edges of the phyllaries are often rolled under and thus may appear needle-like. The phyllaries and the bracts attached to the panicle branches both have a tiny spine at their tip. (Note: heath aster (S. ericoides) also has such spines but has smaller flowerheads, broad, blunt phyllaries with a larger spine, and the hairs on the stems are either appressed to the stem or are ascending.) The fruits are 1-1.15 mm long, tan colored, dry seeds with 3-4 longitudinal ribs and a tuft of white hairs. After blooming is completed, rosettes of 3" long, 1" wide, spoon-shaped basal leaves develop and persist through the winter into the spring, but wither away before blooming begins again.

Symphyotrichum

Symphyotrichum pilosum

hairy aster [Blooms: Aug – Nov]

The panicles of Short's aster's flowerheads are up to 18" long and 8" across; the panicles arise from the tips of the central stem and the upper lateral branches. The flowering branches are long, widely spreading or arching, and covered with small, leaf-like bracts and stiff hairs. Individual flowerheads are 3/4-1" across. Flowerheads consist of 10-20 lavender or pale blue-violet (rarely white) ray florets and 15-23 disk florets, initially yellow but becoming reddish purple over time. The phyllaries that surround the base of the flowerheads are covered with stiff, white appressed hairs, are whitish or light green with a diagnostic dark green, diamond-shaped tip, and sometimes also with a dark green medial vein. The fruits are 2-3 mm long, oblong-shaped, with a tuft of light brown hairs at one end. The indented bases of the lower and middle leaves, the slender, wingless petiole, the hairless leaves, and the phyllaries with dark green apical diamonds together are good indicators of Short's aster. Short's aster is the commonest aster in bloom in Jackson Park in early autumn; later in the autumn it is overtaken in numbers (or at least visual impact) by New England asters.

Symphyotrichum

Symphyotrichum shortii

Short's aster [Blooms: Aug – Nov]

The upper stems and branches (some arising from upper leaf axils) of white arrowleaf aster terminate in 6-18" long panicles of flowerheads; the panicles are 2-3 times longer than wide. Each flowerhead is 1/2-3/4" across with 8-15 pistillate, white (rarely pale lavender) ray florets and 10-15 perfect (both stamens and styles present) disk florets. The disc florets are initially yellow but turn pink or light purple with age such that the flowerheads with yellow disk florets are often in the minority on the plant. The individual disk florets strike me as being larger than on many asters. The phyllaries (bracts) covering the base of the flowerhead are narrowly lance-shaped, usually hairless, dark green in the middle tapering to narrow, stiff, green to purplish tips. The fruits are 2 mm long, purplish-brown dry seeds with longitudinal ribs and a tuft of hairs at one end. White arrowleaf aster is similar to Drummond's aster (Symphyotrichum drummondii) but is less hairy and has distinctly different phyllaries. Among asters with white flowerheads, only white arrowleaf aster has heart-shaped leaves. (Other asters with heart-shaped leaves typically have blue to violet flowers.)

Symphyotrichum

Symphyotrichum urophyllum

white arrowleaf aster [Blooms: Aug/Sep – ?]

Immediately above the terminal stem leaves or leaflets of rue anemons is an umbel of one to six 1/2-1" flowers on 1.5" long pedicels. Each flower has 5-10 white or pinkish-white, petal-like sepals and a striking green center made of 1-16 pistils surrounded by 7-30 stamens with yellow anthers. There are no true petals. The fruit is a cluster of 5-15 strongly ribbed spindles about 8 mm long, pointed at both ends; each contains a single seed. Rue anemone prefers woodlands with dappled sunlight in the spring but tolerates shade in the summer months. The leaflets/leaves of rue anemone are similar to the leaflets of purple meadow-rue (Thalictrum dasycarpum), but you'll never confuse the two; purple meadow-rue blooms six weeks later and is seven feet taller than rue anemone.

Thalictrum

Thalictrum thalictroides

rue anemone [Apr – May]

Western goat's-beard's stems terminate in a single flowerhead, with the stem strongly swollen beneath the flowerhead. Individual flowerheads are pale lemon yellow and about 2" across. Between 50-180 ray florets are present; disc florets are absent. A series of about 13 sharply pointed, narrow bluish-green bracts (significantly longer than the outer ray florets) surround the base of the flowerhead. The outer ray florets (the "petals") are much longer than the inner ray florets. All ray florets have an outer tip of the "petal" decorated with five small teeth. Near the base of the ray florets is a composite reproductive structure consisting of a single style, bifurcated at its tip, and five stamens with black anthers closely appressed to the middle of the style. The flowerheads open in the morning but close in the afternoon; the flowerheads sometimes track the sun like a sunflower. Fertilized florets produce a long, narrow, naked seed densely covered with small teeth; the seed is attached to a plume of fine white hairs (like a dandelion). The seed head looks like a giant version of a dandelion seed head. Western goat's beard is very similar to yellow goat's beard (Tragopogon pratensis) but prefers drier habitats; the latter has only eight bracts (rather than 13) surrounding the flowerhead and the bracts are the same length (not longer) than the outer ray florets.

Tragopogon

Tragopogon dubius

western goat's-beard [Blooms: May-Sep]

Yellow goat's-beard stems produce a long naked stalk from their tips that bears a single flowerhead. Individual flowerheads are bright yellow and 1-2.5" across. Between 50-180 ray florets are present; disc florets are absent. A series of about eight sharply pointed, narrow green bracts (the same length or shorter than the outer ray florets) surround the base of the flowerhead. The outer ray florets (the "petals") are much longer than the inner ray florets. All ray florets have an outer tip decorated with five small teeth. Near the base of the ray florets is a composite reproductive structure consisting of a single yellow style, bifurcated at its tip, and five stamens with black anthers closely appressed to the middle of the style. Fertilized florets produce a long, narrow naked seed; the seed is attached to a plume of fine white hairs (like a dandelion). The seed head looks like a giant (3" across) version of a dandelion seed head. Like Tragopogon dubius, it's an exotic, but at least it's less aggressive. Distinguish yellow goat's beard (T. pratensis) from western goat's beard (T. dubius) by flower color (bright yellow vs. pale yellow), foliage color (green vs. bluish green, number of floral bracts (8 vs. 13), leaf shape (tips curled vs. tips straight), and length of the floral bracts (same as petals vs. much longer than petals).

Tragopogon

Tragopogon pratensis

yellow goat's-beard [Blooms: May-Aug]

The top of the wingstem plant is a dome (a panicle) of coarse-looking flowerheads. Each flowerhead is 1-2" across, with 2-10 yellow, oblong, drooping petals, 1/2-1" long that are derived from the sterile ray florets. Some 40-60+ yellowish-green, tubular disk florets project in all directions in a hemisphere of widely-spaced, robust, bud-like blunt cylinders, the tips of the disk florets. When receptive to pollen, the disk florets bear a protruding style with a bifurcated, curling pair of stigmas (likened by one source to a "pince-nez" — a pair of eyeglasses on a handle); the five stamens and their flattened, black anthers are appressed to the body of the style. The fruit is a teardrop-shaped seed with a pair of thin wings and two short, robust, spiky awns. Immature seeds are green; the seeds (and seedheads) turn brown when mature.

Verbesina

Verbesina alternifolia

wingstem [Blooms: Jul-Oct]