Stout, rhizomatous perennial, decumbent to suberect, to 1 m; stipules foliaceous, broadly ovate, 1.5-4 נ1-2.5 cm, symmetrical, with 2 ±well developed basal lobes; lfls 3-6 pairs, somewhat fleshy, oblong to obovate, 3-5 cm, half as wide; peduncles equaling or shorter than the subtending lvs, with usually 5-10 purple fls (1.2-)1.5-2.5(-3) cm; cal irregular, the lowest lobe lance-linear, nearly twice as long as the triangular upper ones; 2n=24. Sea-beaches and lake-shores; circumboreal, in our range s. on the Atlantic coast to N.J., on the shores of Lake Champlain, Oneida Lake, N.Y., and the Great Lakes. June-Aug. (L. japonicus) Glabrous plants, in our range abundant on the Great Lakes and occasional along the seacoast, are var. glaber (Ser.) Eames. Plants pubescent at least on the cal, pedicels, and lower lf-surface, abundant on the coast and very rare on the Great Lakes, are var. pellitus (Fernald) Gleason.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.