Ballota nigra subsp. nigra

Tutin, T. G., Heywood, V. H., Burges, N. A., Moore, D. M., Valentine, D. H., Walters, S. M. & Webb, D. A., 1972, Flora Europaea. Volume 3. Diapensiacea to Myoporaceae, Cambridge: Cambridge University Press : 150

(a) Subsp. nigra

( B. nigra subsp. ruderalis (Swartz) Briq. ):

Pubescent to subglabrous, with papillae and non-shining glands. Stems up to 120 cm; lower intemodes up to 10 cm, the upper shorter. Petiole up to 50 mm. Calyx 9-13 mm; lobes (3-)4- 6-5 mm, erect, triangular- to subulate-lanceolate, awned; awn 1 - 5-3 mm. Corolla 12-14 mm, lilac. Europe from Sweden, Germany and Albania eastwards; naturalized in N.W. Europe.