Sonchus L.

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1976, Flora Europaea. Volume 4. Plantaginaceae to Compositae (and Rubiaceae), Cambridge University Press : 327

166. Sonchus L. 1

Annual, biennial or perennial herbs, rarely woody at the base. Stems usually solitary, usually branched. Leaves denticulate to pinnatisect, often spiny, the cauline amplexicaul. Capitula few to numerous. Involucral bracts in 3 imbricate rows. Receptacle without scales. Ligules yellow. Achenes compressed, narrowed at both ends, with 1-4 ribs on each face, not beaked; pappus of 2 kinds of hairs: deciduous, rough solitary hairs and more or less persistent, softer hairs in fascicles.

1 Stem woody at base; achenes 3-5-5 mm 8. pustulatus 1 Stem not woody; achenes 2-3-75 mm

2 Annual or biennial

3 Achenessmoothat leastbetween the ribs,stronglycompres­

sed and ± winged 1. asper 3 Achenesrugoseor tuberculatebetweentheribs,neither strongly compressed nor winged

4 Leaf-lobes strongly constricted at base, or narrowly linear; terminal lobe usually about as large as the lateral lobes; ligules longer than corolla-tube; achenes abruptly contracted at base 2. tenerrimus 4 Leaf-lobes (if present) not constricted at base; terminal lobe usually much larger than the lateral lobes; ligules about as long as corolla-tube; achenes gradually narrowed at base 3. oleraceus 2 Perennial

5 Capitulasubsessile;leaveswithstrong marginalspines

6. crassifolius 5 Capituladistinctlypedunculate;leavesnotor weaklyspiny

6 Leaf-lobes strongly constricted at base, or narrowly linear

2. tenerrimus 6 Leaf-lobes (if present) not constricted at base, not narrowly linear

7 Auricles of cauline leaves lanceolate, acute, denticulate

5. palustris 7 Auricles of cauline leaves rounded, often dentate

8 Achenes strongly transversely rugose; capitula glandular-hairy or glabrous 7. arvensis 8 Achenes not or weakly transversely rugose; capitula glabrous or eglandular-tomentose at base 4. maritimus