This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Annual or perennial succulent herbs, with alternate, mostly auriculate-clasping, entire dentate lobed or pinnatifid, prickly-margined leaves, and large or middle-sized, peduncled corymbose or paniculate heads of yellow flowers. Involucre ovoid or campanulate, usually becoming thickened and more or less conic at the base when old, its bracts herbaceous or membranous, imbricated in several series, the outer successively smaller. Receptacle flat, naked. Rays truncate and 5-toothed at the apex. Anthers sagittate at the base. Style-branches slender. Achenes oval, oblong, or linear, more or less flattened, 10-20-ribbed, somewhat narrowed at the base, truncate. Pappus of very copious soft white simple capillary bristles, usually falling away connected, sometimes with 1 or 2 stouter ones which fall separately. [The Greek name of the Sow-thistle.]
About 45 species, natives of the Old World. Besides the following, another occurs on the Pacific Coast. Type species: Sonchus oleraceus L.
Involucre glandular-pubescent; heads nearly 1 high.
1. S. arvensis.
Involucre glabrous; heads 6-8" high.
Auricles of the leaves acute; achenes striate and transversely wrinkled.
2. S. oleraceus.
Auricles rounded; achenes ribbed, not transversely wrinkled.
3. S. asper.
Sonchus arvensis L. Sp. Pl. 793. 1753.
Perennial by deep roots and creeping rootstocks, glabrous; stem leafy below, paniculately branched and nearly naked above, 2°-4° high. Lower and basal leaves runcinate-pinnatifid, often 12' long, spinulose-dentate, narrowed into short petioles, the upper pinnatifid or entire, lanceolate, clasping; heads several or numerous, corymbose-paniculate, 1'-2' broad, bright yellow, very showy; involucre nearly 1' high, its bracts as also the peduncles glandular-bristly; achenes oblong, compressed, with about 10 rugose longitudinal ribs.
In low grounds, fields and waste places. New Jersey to Quebec, Newfoundland, Minnesota, Colorado and British Columbia. Naturalized from Europe. Native also of Asia. July-Oct. Dindle. Gutweed. Swine-thistle. Tree sow-thistle.
Fig. 4066. Sonchus Oleraceus L. Sp. Pl. 794. 1753
Annual, with fibrous roots; stem leafy below, nearly simple, i°-io° high. Basal and lower leaves petioled, lyrate-pinnatifid, 4'-10' long, the terminal segment commonly large and triangular, the margins denticulate with mucronate or scarcely spiny teeth; upper leaves pinnatifid, clasping by an auricled or sagittate base, the auricles acute or acuminate; uppermost leaves often lanceolate and entire; heads several or numerous, pale yellow, 9"-15" broad; involucre glabrous, 6"-8" high; achenes flat, longitudinally ribbed and transversely rugose.
In fields and waste places, a common weed in most cultivated parts of the globe except the extreme north. Also in Central and South America. Naturalized from Europe. Hare's-colewort or -thistle. Milk-weed. Milk-thistle. Milky tassel. Swinies. The leaves used as a salad and as a pot herb. May-Nov.
Sonchus oleraceus var. asper L. Sp. Pl. 794. 1753. Sonchus asper Hill, Herb. Brit. 47. 1769.
Annual, similar to the preceding species; leaves undivided, lobed or sometimes pinnatifid, spinulose-dentate to spinulose-denticulate, the lower and basal ones obovate or spatulate, petioled, the upper oblong or lanceolate, clasping by an auricled base, the auricles rounded; heads several or numerous, 1' broad or less; flowers pale yellow; involucre glabrous, about 6" high; achenes flat, longitudinally ribbed.
In waste places throughout most of our area and in tropical and South America. Widely distributed as a weed in nearly all cultivated parts of the earth. Naturalized from Europe. May-Nov.