Perennial 4-8 dm; lvs broadly ovate-oblong to deltoid, 5-10 cm, coarsely and irregularly serrate, truncate or more often subcordate at base, sparsely hirsutulous, long-petioled; infls usually several, 1-2 dm, interrupted, with 12-30 fls per node; cal almost tubular, 6 mm at anthesis, the upper lip shortly 3-lobed, a fourth to a third as long as the tube and about equaling the lower lip; cor blue (white), 10-15 mm, its upper lip narrowed to the base; 2n=16. Native of s. and e. Europe and w. Asia, intr. in fields and waste places here and there in our range. July-Sept.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.