Erect, often freely branched perennial 4-12 dm from a cluster of fleshy-fibrous roots; lvs alternate, lanceolate or lance-linear, acute or acuminate, 5-10 cm, tapering to the sessile or subpetiolar base; pedicels 3-5 mm, with 2 lanceolate bracteoles near the top; fls 4-merous; pet about equaling the sep; stamens 4; fr 5-6 mm, glabrous or hairy, nearly cubic, with rounded base, slightly wing-angled, opening by a terminal pore, and eventually loculicidal; pedicels to about as long as the fr; 2n=16. Swamps and wet soil; Mass. and s. Ont. to Io. and s. Neb., s. to Fla. and Tex. July, Aug. Ozarkian plants, extending e. to s. Ind., tend to be evidently short-hairy, and have been distinguished from the more eastern or northern, essentially glabrous plants, as var. pubescens E. J. Palmer & Steyerm.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.