Erect, fibrous-rooted perennial 5-15 dm, the roots bearing small tubers; lower lvs long-petioled, cordate-ovate, 1-2 dm, coarsely crenate, the others progressively reduced and less petiolate, the bracteal ones subsessile; spikes 1-3 dm; each verticil subtended by numerous subulate bracts 1 mm; cal-tube 1 cm, hirsute on the nerves, the lobes 2-3.5 mm; cor purple, 2 cm; 2n=22. Native of Eurasia, naturalized in w. N.Y. June-Sept.

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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