Fibrous-rooted, shortly rhizomatous perennial to 8 dm, simple or branched above, pilose-hirsute, especially above, with hairs 1-3 mm (seldom subglabrous); lvs lanceolate or lance-elliptic, 3-10 נ0.5-2.5 cm, mostly sessile, acute or acuminate, remotely denticulate or dentate or entire; infl compact, many-fld, the buds erect; fls diurnal, out- crossing, hypanthium (1-)1.5-2.5 cm; sep 1-2 cm, their free tips 1-3 mm; pet (1-)1.5-2.5 cm, notched at the summit; filaments alternately unequal; anthers 4-8 mm; style 10-20 mm; fr elliptic or linear-elliptic to rather narrowly clavate, the body 8-15 mm, tapering to a sessile or shortly pedicel-like base; 2n=56. Moist soil, wet meadows, fields, and open woods; Io. and s. Wis. to La., e. to s. Ont., w. N.Y., and w. W.Va., and occasionally escaped as far e. as Vt., Mass., and Va. May-July. (O. pratensis; Kneiffia p.; O. fruticosa var. hirsuta)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.