Culms 12-80 cm. Leaves 2-6 per culm; sheaths tight, inner band hyaline, 3.5-21 cm, apex concave, glabrous; ligules rounded, 0.8-1.8 × 0.6-1.6 mm; blades involute, 4-70 cm × 0.4-1.5 mm, widest leaf 0.8-1.5 mm wide. Inflorescences 0.6-4 cm; spike 1 (occasionally 1-3 smaller accessory spikes), gynecandrous with staminate portion of spike 1-3 mm wide, to 50-flowered and pistillate portion of spike 5-9.5 mm wide, to 27-flowered or plants sometimes unisexual with staminate and pistillate spikes on different plants. Pistillate scales ovate, 1.8-3.3 × 1.3-2.2 mm, apex acute. Staminate scales lanceolate to ovate, 1.7-5.5 × 1-2.2 mm, apex acute. Anthers (2-)2.2-3.6 mm. Perigynia spreading to reflexed, castaneous to dark brown, 15-veined abaxially, faintly 7-veined adaxially, lanceolate-ovate to broadly ovate, 2.6-4.7 × 1.25-2.3 mm, 1.3-2.65 times as long as wide; beak 0.5-1.7 mm, 0.2-0.65 length of body, serrulate, teeth blunt, to 0.35 mm, soft. Achenes ovate, 1.4-2.2 × 1.2-1.7 mm. Fruiting late spring-early summer. Fens, bogs; 0-500 m; St. Pierre and Miquelon; N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que.; Ala., Del., Maine, Md., Mass, Mich., Minn., Miss., N.H., N.J., N.Y., N.C., R.I., Vt., Wis.
Densely tufted, the stiff, smooth stems 2-7 dm, usually surpassing the slender, involute lvs; spike usually solitary, 0.8-2.5(-4) cm, gynaecandrous or unisexual; lateral spikes 1 or 2 and much smaller, or usually none; lower 2 scales empty and erect; anthers 2-3.5 mm; pistillate scales ovate, about equaling the body of the perigynium, usually acute, reddish-brown with hyaline margins; perigynia to ca 25, at least the lower ones spreading or reflexed, castaneous, planoconvex, ovate, 2.6-4.7 mm, spongy- thickened at base, with to 15 faint nerves dorsally and to 7 ventrally, the serrulate-margined beak a fifth to two-thirds as long as the body; achene lenticular; 2n=ca 62. Sphagnum-bogs and other open, wet, low places; Lab. and Nf. to Del. and Md., w. to Ont., n. Mich., and n. Minn.; disjunct in N.C. and Miss.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.