A usually densely velvety native of Europe, is rarely adventive with us. It has smaller lvs (commonly 1-2.5 cm) with only 2-3 pairs of lateral veins, those of the infl often somewhat reduced; it differs from all our other spp. in having the cal hairy in the throat and with distinctly unequal teeth.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.