Cespitose perennial from short rhizomes; stems to 1.5 m, sometimes with nodal bulblets; lvs 10–20, the main blades 3–8 mm wide; infl widely twice or thrice branched, usually with bulblets at base; spikelets broadly ovate, 3–4 mm, sessile in numerous small glomerules; scales rotund, mucronate, with conspicuous green midstrip and red-brown or red-purple sides; bristles 6, brown, surpassing the achene, straight and smooth below, contorted and retrorsely barbellate above; style trifid; achenes 1.1–1.3 mm, obovate or nearly obtriangular, compressed-trigonous; 2n=58. Swamps and marshes; Mass. and Vt. to Ill. and s. Mo., s. to Ga. and Ala. Fr July, Aug.