Perennial 3-7 dm; lvs denticulate, hirtellous, the lower petioled, lance-oblong, the upper ovate to narrowly triangular, sessile and ±clasping; fls sessile in terminal glomerules subtended by leafy bracts, or a few sessile in the axils of the uppermost lvs; sep narrowly lanceolate, 6-10 mm; cor blue-violet, 2-3 cm; 2n=34, 68. Native of Eurasia, escaped from cult. into roadsides and waste places in N. Engl. and adj. Can., w. to Minn. June, July.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.