47. Sonchus L. (sow thistle)

(Boulos, 1972, 1973, 1974a, b; Pons and Boulos, 1972; Roux and Boulos, 1972)

Plants annual, biennial, or perennial herbs, taprooted or with rhizomes. Latex white. Stems 1 or few, erect or ascending, unbranched or branched, finely to relatively coarsely ridged, usually hollow between the nodes, glabrous below the inflorescence (rarely stalked-glandular in S. asper). Leaves alternate and basal, mostly 4–20 times as long as wide, glabrous or the undersurface rarely sparsely pubescent with minute, inconspicuous, unbranched hairs, sessile or the basal leaves with short to long, winged petioles, the basal leaves usually persistent at flowering, the stem leaves with a pair of prominent lobes clasping the stem. Leaf blades shallowly to deeply and often irregularly pinnately lobed, narrowly oblong-lanceolate to lanceolate, oblanceolate, or less commonly obovate in outline, the margins with sharp, spreading teeth, these often irregular and prickly at the tips. Inflorescences terminal panicles, the heads solitary or more commonly in loose clusters at the branch tips, sometimes reduced to a solitary terminal cluster of heads. Involucre becoming slightly but not noticeably elongated as the fruits mature, ovoid to pear-shaped at early flowering, usually becoming cup-shaped or somewhat bell-shaped by late flowering or fruiting, the bracts 1 inner and 3 or 4 outer series, often somewhat thickened toward the base, glabrous or sparsely to moderately pubescent with spreading, gland-tipped hairs, occasionally with minute, branched, cobwebby to woolly hairs toward the base, sometimes darkened or purplish-tinged toward the tip, those of the outer series 17–25, overlapping and varying from much shorter than to nearly as long as the inner series, linear to narrowly lanceolate; those of the inner series more or less equal, 15–27, narrowly oblong-lanceolate, tapered to a sharply pointed tip, the tip appressed-ascending to loosely ascending at flowering. Receptacle naked, usually minutely pitted at the base of each floret. Ligulate florets 80–250 or more per head. Corollas light yellow to orangish yellow. Pappus of numerous apparently smooth (microscopically barbed) bristles, these white, often shed irregularly at fruiting. Fruits with the body oblong-elliptic to elliptic or oblanceolate in outline, flattened, not beaked, the pappus attached to an unexpanded, unmodified tip, with 3 to several longitudinal nerves or ridges on each face, sometimes also finely cross-wrinkled. Fifty to 70 species, Europe, Asia, Africa, introduced widely.