This ubiquitous weed is found in temperate latitudes throughout the world. The tight little flower heads never open up any wider than what you see here. These plants, growing on a sunny and recently disturbed bank in Beechview, were among the very earliest flowers to bloom in the spring; this picture, in fact, was taken on March 20, the first day of spring.

Gray’s description of the genus and species follows, but it does not describe the plants in the photograph very well. The on-line Flora of North America remarks that the plants may be “sparsely tomentose when young,” as these plants were. And although Gray gives “July-Sept” as the flowering period, the Flora of North America says “flowering early spring.” In fact these can also be seen very late in the fall, and almost any time in between. The plant blooms very quickly from seed, and seedlings can overwinter; and it seems to present very different habits depending on the time of year.

SENECIO [Tourn.] L. Groundsel. Ragwort. Squaw-weed. Heads many-flowered; rays pistillate or none; involucre cylindrical to bellshaped, simple or with a few bractlets at the base, the bracts erect-connivent. Receptacle flat, naked. Pappus of numerous very soft and capillary bristles.— Ours herbs, with alternate leaves and solitary or corymbed heads. Flowers chiefly yellow. (Name from senex, an old man, alluding to the hoariness of many species, or to the white hairs of the pappus.)

Annuals (rarely becoming biennial); stems leafy to the Inflorescence; heads medium-sized, 1 сш. or less high during anthesis.

S. vulgàris L. (Common Groundsel.) Low annual, 1-6 dm. high. corymbosely branched, glabrate, leafy to the inflorescence; leaves pinnatifid and toothed, 1-8 cm. long, 0.6-3 cm. broad; calyculate bracts (bracteoles) of the involucre distinctly black-tipped; rays none; achenes hirtellous. — Waste grounds, common. July-Sept. (Nat. from Eu.)

The white form of the Zigzag Aster (for which the preferred botanical name is now Symphyotrichum prenanthoides) is not terribly rare, though far less common than the blue form. Here we see the white form in the foreground, and the blue in the background. All shades between pale blue and white occur, so it’s very hard to mark where blue ends and white begins.

This plant was growing along a trail in Bethel Park, where it was blooming in early October.

We repeat the description we gave when we presented the blue form:

Flowers. Heads about an inch and a quarter wide, in irregular corymbs; disk flowers yellow, fading to red-brown; rays pale blue or violet, sometimes white, linear, numerous.

Leaves. Variable: alternate; lanceolate or ovate-lanceolate, with sharp and narrow points; strong central rib; rough, outward-facing hairs noticeable when rubbed toward stem; lower leaves on petioles with broad wings clasping the stem; upper sessile and clasping. On some plants the leaves are jaggedly toothed; on others the teeth are less prominent, with the upper leaves almost entire.

Stem. Tough, wiry; with purplish vertical lines; arching, about 1 or 2 feet high; characteristically zigzag from leaf to leaf, as in the picture at right.

Gray describes the genus Aster and the species:

ÁSTER [Tourn.] L. STARWORT. FROST-FLOWER. ASTER. Heads many-flowered, radiate; the ray-flowers in a single series, fertile. Bracts of the involucre mure or less imbricated, usually with herbaceous or leaflike tips. Receptacle flat, alveolate. Achenes more or less flattened; pappus simple, of capillary bristles (double in §§ 4 and 5). — Perennial herbs (annual only in §§ 7 and 8), with corymbed, panicled, or racemose heads, flowering chiefly in autumn. Rays white, purple, blue, or pink; the disk yellow, often changing to purple. Species often without sharply defined limits, freely hybridizing. (Name aster, a star, from the radiate heads of flowers. )

A. prenanthoìdes Muhl. Stem 1 m. or less high, corymbose-panicled, hairy above in lines; leaves rough above, smooth underneath, ovate to lanceolate, sharply cut-toothed in the middle, conspicuously taper-pointed, and rathrr abruptly narrowed to a long contracted entire portion, which is abruptly dilated into a conspicuously auricled base; heads on short divergent peduncles; involucre 5-8 mm. high; bracts narrowly linear, tips recurved-spreading; rays violet. — Borders of streams and rich woods, w. N. E. to Va. and Ky., w. to Minn, and la. Aug.-Oct.

Now Symphyotrichum prenanthoides. This is probably our most common roadside blue aster. The Zigzag Aster is so named from its crooked stem (which also gives it the name “Crooked-Stemmed Aster”).This plat was growing along a trail in Bethel Park, where it was blooming in early October.

Asters laugh at the notion of “species,” as Gray notes in his description of the genus, so it’s always best to regard any identification, even a fairly sure one like this, as tentative.

Flowers. Heads about an inch and a quarter wide, in irregular corymbs; disk flowers yellow, fading to red-brown; rays pale blue or violet, sometimes white, linear, numerous.

Leaves. Variable: alternate; lanceolate or ovate-lanceolate, with sharp and narrow points; strong central rib; rough, outward-facing hairs noticeable when rubbed toward stem; lower leaves on petioles with broad wings clasping the stem; upper sessile and clasping. On some plants the leaves are jaggedly toothed; on others the teeth are less prominent, with the upper leaves almost entire.

Stem. Tough, wiry; with purplish vertical lines; arching, about 1 or 2 feet high; characteristically zigzag from leaf to leaf, as in the picture at right.

Gray describes the genus Aster and the species:

ÁSTER [Tourn.] L. STARWORT. FROST-FLOWER. ASTER. Heads many-flowered, radiate; the ray-flowers in a single series, fertile. Bracts of the involucre mure or less imbricated, usually with herbaceous or leaflike tips. Receptacle flat, alveolate. Achenes more or less flattened; pappus simple, of capillary bristles (double in §§ 4 and 5). — Perennial herbs (annual only in §§ 7 and 8), with corymbed, panicled, or racemose heads, flowering chiefly in autumn. Rays white, purple, blue, or pink; the disk yellow, often changing to purple. Species often without sharply defined limits, freely hybridizing. (Name aster, a star, from the radiate heads of flowers. )

A. prenanthoìdes Muhl. Stem 1 m. or less high, corymbose-panicled, hairy above in lines; leaves rough above, smooth underneath, ovate to lanceolate, sharply cut-toothed in the middle, conspicuously taper-pointed, and rathrr abruptly narrowed to a long contracted entire portion, which is abruptly dilated into a conspicuously auricled base; heads on short divergent peduncles; involucre 5-8 mm. high; bracts narrowly linear, tips recurved-spreading; rays violet. — Borders of streams and rich woods, w. N. E. to Va. and Ky., w. to Minn, and la. Aug.-Oct.