Stem stout, to 3 mm thick; internodes seldom over 1.5 cm; lvs whorled, (1.5-)2-4 cm, pinnatisect into capillary segments; spikes emersed, 5-15(-40) cm; bracts whorled, persistent and eventually reflexed, lanceolate to oblong or even obovate, sharply serrulate, 4-18 mm (but fairly uniform on each plant); stamens 4; fr subglobose, 1-1.5 mm, each mericarp rounded or more commonly with 2 low keels on the back, scabrous to obscurely tuberculate, with an ascending- recurved beak. N.Y. to w. Ont. and N.D., s. to Fla. and Tex., more abundant southward.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.