Lonicera caerulea subsp. caerulea

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 : 46

(a) Subsp. caerulea :

Twigs glabrous or sparsely hairy. Leaves glabrous or slightly hairy beneath, mostly along midrib. Corollatube wide, about twice as long as the limb. 2n = 18. Throughout the range of the species, but rare in the north-east.