Culms 10-90(-135) cm. Leaves 3-6 per culm; sheaths tight, inner band hyaline, 1.8-2.5 cm, apex concave, glabrous; ligules 0.6-2.5(-4.5) mm, rounded to ± acute; blades plicate, 5-40 cm × 0.7-3.3(-3.8) mm, widest leaf 1-3.3(-3.8) mm wide. Inflorescences 0.7-7.8 cm; spikes (2-)3-8; lateral spikes pistillate often with few staminate flowers proximally, 3-15.5 mm, sessile, staminate portion 7-flowered, to 8.2 mm, pistillate portion 3-32-flowered, 2.5-11 mm; basal 2 spikes 1.7-42 mm apart; terminal spike gynecandrous, 5-24 mm, staminate portion 2-17-flowered, 2-16.5 × 0.9-2 mm, pistillate portion 4-26-flowered, 2.6-9 × 4.9-9.1 mm. Pistillate scales ovate, (1.4-)2.1-3.1 × 0.7-2.3 mm, apex acute to sometimes obtuse. Staminate scales ovate-lanceolate to ovate, 1.3-3.8 × 0.8-1.7 mm, base clavate, apex acute. Anthers 0.8-1.6(-2) mm. Perigynia spreading to reflexed, castaneous to dark brown, 2-14-veined abaxially, 0-12-veined adaxially over achene, lanceolate to ovate, (2.65-)2.9-4.75 × 0.8-2.1 mm, (1.7-)1.8-3.2(-3.6) times as long as wide; beak (0.85-)0.95-2 mm, (0.4-)0.45-0.86 length of body, serrulate, teeth (0-)0.15-0.5 mm. Achenes ovate-lanceolate to rhombic-ovate, 1.3-2.1 × 0.8-1.55 mm. 2n = 58.
Stems densely tufted, aphyllopodic, 1-6 dm, scabrous on the angles above; lvs 3-6 per stem, all in the basal third, to about as long as the stems, plicate, mostly 1-2.5 mm wide; spikes 3-7, sessile, small and few-fld, the terminal one with a conspicuous, slender, staminate base, some of the lateral ones often wholly pistillate; bracts small and inconspicuous; anthers 0.8-1.6 mm; perigynia 5-15, crowded, widely spreading or the lower reflexed, green or tan, planoconvex, spongy-thickened at base, lightly several- to many-nerved dorsally, few- to several-nerved or virtually nerveless ventrally, narrowly lance-triangular to move commonly lance-ovate or even ovate, 2.8-3.5(-4) mm, 1.8-3.2 times as long as wide, often serrulate-margined distally, with a prominent, slender, serrulate-margined, sharply bidentate beak 1-1.6 mm, half as long to almost as long as the body; achene lenticular; 2n=50-58. Swamps, bogs, and other wet places; circumboreal, s. to Va. (and in the mts. to N.C.), Ind., Io., Utah, and Calif. Ours is the widespread var. echinata. (C. angustior; C. cephalantha; C. josselynii; C. laricina; C. muricata, misapplied; C. stellulata)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.