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.
A herb which forms clumps by suckering. It grows 30-90 cm high and spreads 30-60 cm wide. The stems have bristles. The leaves at the base have long leaf stalks. The leaves are 8 cm long and have fine teeth around the edge. The leaves on the stem do not have stalks. They are smaller and clasp the stem. The flowers are blue and in round heads at the tips of the plant. They can also be in the axils of the leaves.