Sonchus oleraceus L.
sow thistle
Annual. Roots tap and fibrous. Stem erect, simple or branched, finely grooved or ribbed, glabrous, 50-120 cm tall. Lvs soft, dull to ± shiny, mid to dark green to glaucous above, pale to glaucous beneath, glabrous, ± oblanceolate to obovate; margins dentate with spinulose teeth. Rosette and lower stem lvs (4)-10-20 × (1.5)-4-10 cm, pinnatifid almost to midrib; lobes reflexed or recurved, ovate to narrowly triangular; petiole narrowly winged. Upper lvs pinnatifid, usually with broadly triangular terminal lobe, 1-3 pairs of narrowly triangular lateral lobes, a broadly expanded winged petiole, and an amplexicaul-auriculate base with pointed lobes, sometimes lf not lobed, ovate-amplexicaul, rarely pinnatisect with linear lobes. Infl. cymose to umbellate; capitula few to many. Involucre 10-15 mm long, turbinate to cylindric; bracts imbricate, reflexed at fruiting, usually glabrous or rarely with a few pale glandular or eglandular setae. Receptacle glabrous. Florets 11/2× length of involucre; corolla tube c. = ligule; ligules spreading, yellow. Achenes narrowly obovoid to clavate, brown, weakly flattened, 2.5-3 × 0.8-1 mm, 3-ribbed on each face, not winged; ribs and spaces between finely transversely wrinkled. Pappus fine, white, c. = involucre.
N.; S.; St.; K., Ch., A., C.: throughout.
Europe, N. Africa, N. and W. Asia 1832
Waste land, grassland, coastal rocks, dunes and beaches, forest margins, crevices in walls and footpaths, gardens, pasture, roadsides, railway land.
One specimen (CHR 79353, Earnscleugh, McNeur, 2.3.1950) was identified as S. tenerrimus L. by Boulos. Although it has the ligule slightly > corolla tube, its involucre and peduncles are glabrous and its achenes are gradually narrowed to the base, features of S. oleraceus.
