Ononis spinosa subsp. spinosa

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1981, Flora Europaea. Volume 2. Rosaceae to Umbelliferae, Cambridge University Press : 147

(a) Subsp. spinosa ( O. campestris Koch & Ziz ): Stems erect, usually spiny and with two opposite rows of hairs when young. Leaflets ovate-oblong, acute, more than 3 times as long as wide. Flowers borne singly at each node; corolla 10-20 mm. In the northern part of the range of the species, southwards to S. Italy and N.E. Portugal.