Aster tripolium subsp. tripolium

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 : 115

(a) Subsp. tripolium :

Plant usually rather strongly succulent. Ligules sometimes absent. Achenes of outer florets as long as those of the inner. 2n = 18. Coasts of N. & W. Europe.