Silphium 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 : 142

47. Silphium L. 2

Perennials. Leaves simple, opposite. Capitula medium. Involucral bracts in several rows. Receptacle flat, with numerous scales which are folded round the achenes. Ligulate florets in 2-3 rows, female, yellow. Tubular florets functionally male, yellow. Achenes strongly compressed and winged above. Pappus almost obsolete.