Pls 1-2 m; terminal lfl rotund in outline, 6-15 cm wide, deeply divided into 3-5-ovate or ovate-oblong, serrate segments; lateral lfls 2-5 pairs, 2-8 cm, oblong to ovate, coarsely and sharply doubly serrate, seldom shallowly lobed; sep ovate- triangular, obtuse, pet 5(6) white, 2-5 mm; frs glabrous, 3-4 mm, tightly and spirally imbricated, each going through about a half-turn; 2n=14, 16, 24. Native of Eurasia, occasionally escaped from cult., especially northeastward. June-Aug. Var. ulmaria has the lfls closely tomentose beneath; var. denudata (J. Presl & C. Presl) Beck has the lfls green and sparsely hairy beneath with long straight hairs.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.
