Sonchus oleraceus Linnaeus var. asper Linnaeus, Sp. Pl. 2: 794. 1753; S. spinosus Lamarck.

Herbs 20-50 cm tall, annual. Stem usually unbranched and glabrous below synflorescence. Basal and lower stem leaves extremely variable, obovate, spatulate, or elliptic, 7-13 × 2-5 cm, undivided or ± irregularly pinnatisect, glabrous, adaxially dark green and ± glossy, base attenuate and ± auriculate, margin usually densely spinulosely dentate, apex acute, acuminate, or obtuse; lateral lobes ± triangular, semiorbicular, or elliptic. Middle and upper stem leaves spatulate to lanceolate, base auriculately clasping with conspicuous rounded and appressed auricles, otherwise similar to lower leaves. Synflorescence densely corymbiform, with few to some capitula. Capitula with many florets; peduncle 0.5-5 cm, slender, glabrous or densely glandular hairy. Involucre ± campanulate, ca. 1.2 cm. Phyllaries abaxially glabrous or more rarely glandular hairy, apex acute; outer phyllaries narrowly lanceolate, 1-2 mm wide. Corolla ca. 1 cm. Achene ± broadly obcolumnar, 2-3 mm, strongly compressed, ± winged, between lateral ribs usually with 3 slender ribs on either side, space between slender ribs much wider than ribs, smooth with only lateral ribs usually antrorsely finely spinulose. Pappus ca. 7 mm, ± caducous. Fl. and fr. May-Oct. 2n = 18.

Sonchus asper is naturalized in areas adjacent to China including Afghanistan, Bhutan, India, Japan, Kashmir, Kazakhstan, Korea, Kyrgyzstan, Nepal, Pakistan, Russia, Tajikistan, Thailand, Turkmenistan, Uzbekistan, and Vietnam. The species is also naturalized in sub-Saharan Africa, Asia, Australia, New Guinea, North and South America, and Pacific islands (New Zealand).

Mountain slopes, forest margins, by water, field margins, ruderal areas; 1500-3700 m. Naturalized in Guangxi, Hubei, Jiangsu, Shandong, Sichuan, Taiwan, Xinjiang, Xizang, and Zhejiang [presumably originating from Europe and Mediterranean region].