Plants densely cespitose; rhizomes arching, short. Culms trigonous, 10-40 cm, scabrous proximal to inflorescence. Leaves: basal sheaths gray-brown; distal leaf sheaths concave at mouth; blades 6-9 × 0.4-0.5 mm, much shorter than culms at flowering and fruiting. Inflorescences: spikelets 15-20-flowered, 5.4-8 × 2.2-3.5 mm; bracts equaling or shorter than spikelets, 4.5-7.8 mm, apex mucronate or awned, awn to 3 mm. Spikelets: scales yellow-brown, apex obtuse. Flowers: perianth bristles 6, white, flattened, exceeding achenes by as much as 20 times, smooth; anthers 1.1-1.6 mm. Achenes plano-convex, 1.2-1.6 × 0.5-0.8 mm. 2n = 58.

Fruiting summer (Jun-Aug). Open or shaded, wet, peaty or gravelly fens, bogs, sheltered banks of lakes, ponds, and streams, tending to occur on lime-rich substrates; 0-1400 m; Alta., B.C., Man., N.B., Nfld. and Labr., N.W.T., N.S., Nunavut; Ont., Que., Sask., Yukon; Alaska, Conn., Maine, Mass., Mich., Minn., Mont., N.H., N.J., N.Y., Vt., Wis.; Europe; c Asia (Kamchatka).