Glabrous rhizomatous perennial, to 8 dm; stipules semicordate, 1.5-3 cm, the broadly rounded basal lobe often irregularly toothed; lfls 3-5 pairs, thin, elliptic to lance-ovate or obovate, 2.5-5 cm, racemes shorter than the subtending lf, with 5-10 ochroleucous fls 12-18 mm; cal irregular, the upper lobes triangular, a fourth to half as long as the lower, the lateral lobes broadest distinctly above the base; 2n=14. Dry upland woods and thickets; Vt. to Man. and nw. Can., s. to Pa., Ill., Io., and Wash. May-July.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.