Annuals, biennials, or perennials [shrubs], 3-350+ cm; taprooted, rhizomatous, or stoloniferous. Stems erect, branched distally or throughout, usually glabrous, sometimes stipitate-glandular (mostly distally). Leaves basal and cauline or mostly cauline; basal usually petiolate (petioles usually winged), cauline often sessile; blades mostly oblong, oblanceolate, or lanceolate, (bases often auriculate) margins usually 1(-2)-pinnately lobed, ultimate margins usually dentate (teeth often ± prickly), sometimes entire. Heads borne in corymbiform to subumbelliform arrays. Peduncles not notably dilated distally, usually ± bracteolate, glabrous or stipitate-glandular and/or tomentose. Calyculi 0. Involucres campanulate to urceolate, 5-15+ mm diam. Phyllaries 27-50 in 3-5+ series, unequal, green, deltate to lanceolate or linear, margins sometimes narrowly scarious (sometimes ciliate), apices acute (faces glabrous or stipitate- to setose-glandular). Receptacles flat to convex, ± pitted, glabrous, epaleate. Florets [30-]80-250[-450+]; corollas yellow to orange (not deliquescent; anthers yellowish to brownish apically). Cypselae stramineous or reddish to dark brown, ± compressed, mostly oblong or oblanceoloid to ellipsoid, beaks 0, ribs usually 2-4(-5+) on each face, faces sometimes transversely rugulose or tuberculate, glabrous; pappi tardily falling or persistent, of 80-100+, white, smooth or barbellulate bristles (some flattened, ± setiform scales), outer usually distinct in ± 1 series, inner basally coherent or connate, in 2-3+ series. x = 9. Sonchus species are herbs in North America; some are sometimes woody at bases.
Fls all ligulate and perfect, yellow, few to more often numerous (80+ in all our spp.); invol ovoid or campanulate, rarely narrower, its bracts generally imbricate, occasionally merely calyculate, often basally thickened in age; achenes flattened, 6-20-ribbed, merely narrowed at the tip, beakless, glabrous, often transversely rugulose; pappus of numerous white, capillary, often somewhat crisped bristles that tend to fall connected, and some stouter outer bristles that fall separately; lactiferous herbs with alternate or all basal, entire to dissected, mostly auriculate, often prickly-margined lvs, and solitary to usually several or many, medium-sized to rather large heads in an irregularly corymbose-paniculiform to subumbelliform infl. 50, Old World.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.