48. Sonchus Linnaeus, Sp. Pl. 2: 793. 1753; Gen. Pl. ed. 5, 347. 1754.
Sow-thistle, laiteron [Greek sonchos, ancient name for a kind of thistle]
Philip E. Hyatt
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.
Species 50–60+ (5 in the flora): introduced; Europe (Mediterranean), w Asia, n Africa, Atlantic Islands; some species introduced nearly worldwide.
Sonchus species are herbs in North America; some are sometimes woody at bases.
Boulos, L. 1973. Révision systématique du genre Sonchus L. s.l.: IV. Sous-genre: 1. Sonchus. Bot. Not. 126: 155–196.