Perennials, 0-150(-200) cm, usually rhizomatous or stoloni-ferous. Stem bases hard, some-times ± woody. Leaves: blades of mid cauline oblong to lanceolate, (3-)6-40 × 2-15 cm, bases auriculate, auricles straight or curved, rounded, margins usually pinnately lobed, lobes ± deltate, not constricted at bases, terminals usually larger than laterals, dentate or entire. Peduncles sessile- or stipitate-glandular. Involucres 10-17+ mm. Phyllaries sessile- or stipitate-glandular. Corollas: ligules ± equaling tubes. Cypselae dark brown, oblanceoloid to ellipsoid, 2.5-3.5 mm, ribs 4-5(+) on each face, faces transversely rugulose to tuberculate across and between ribs; pappi 8-14 mm. 2n = 36, 54.

Sonchus arvensis is introduced in temperate regions of all continents. Plants of the species prefer relatively cooler, moister climates and are more abundant in the northern part of North America.

Perennial, 4-20 dm, with long vertical roots and spreading by creeping roots, glabrous at least below the infl and often somewhat glaucous; lvs prickly-margined, the lower and middle ones usually pinnately lobed or pinnatifid, 6-40 נ2-15 cm, becoming less lobed and more auriculate upward, the upper reduced and distant; heads several in an open-corymbiform infl, relatively large, 3-5 cm wide in fl; fls ca 150-235 per head; fruiting invol 14-22 mm; achenes 2.5-3.5 mm, with 5+ prominent ribs on each face, strongly rugulose; 2n=36, 54. A European weed, now widely intr. in temperate N. Am. July-Oct. Var. arvensis is ±copiously provided with coarse, spreading, gland-tipped hairs on the invol and peduncles. Var. glabrescens (G