Rhizomatous perennial with small tubers; stems 2- angled, wingless, to 8 dm; stipules lanceolate, 5-12 mm, with a single short basal lobe; lfls 2, oblanceolate to elliptic, 1.5-3 cm; peduncles 5-8 cm, bearing a crowded raceme of 2-10 red-purple fls 12-16 mm, the standard broader than long; 2n=14. Native of Europe and w. Asia, intr. at a few scattered stations chiefly toward the n. part of our range.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.