Rhizomatous perennial; stems erect, much branched, 5-20 dm, softly and densely villous above; lvs mostly opposite (but the bracts alternate), hairy on both sides, lanceolate or oblong and somewhat clasping, the larger ones 5-12 נ1-3 cm, sharply serrulate, with evident lateral veins; pedicels 1 cm or less; pet red-purple, 10-15 mm, shallowly notched; hypanthium shortly prolonged beyond the ovary; stigma 4-cleft; fr 5-8 cm; coma nearly white; 2n=36. Native of Eurasia and n. Afr., intr. in moist or wet soil, especially in disturbed sites, from s. Me. and s. Que. to Mass. and Md., w. to n. O., Mich., and ne. Ill.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.