Sonchus asper subsp. asper

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

(a) Subsp. asper :

Annual. Leaves mostly cauline, thin, sometimes without spiny margins. Achenes with sparse spinules on margins and ribs. Pollen-grains 35-42 /i. 2л = 18. Almost throughout the range of the species.