Plants densely cespitose, often forming tussocks, short-rhizomatous. Culms to 20(-30) cm. Leaf blades 2-(-10) cm × 0.5-1.5 mm, dead leaf remains often circinnate. Spikes: staminate 2-8 × 0.7-2 mm; pistillate 2-9 × 1-3 mm. Pistillate scales reddish black with hyaline margins, subcircular, 1.4-2.5 × 1.2-2 mm, apex obtuse to subacute, shorter than to as long as perigynium body. Staminate scales reddish black or dark brown, midvein paler, obovate, 2-3 × 0.8-1.4 mm, apex obtuse to acute. Perigynia reddish black to dark brown distally, 1.5-2.5 × 0.9-1.2 mm; beak 0.3-0.5 mm. Achenes obovoid, 1.75 × 0.8 mm. 2n = 34.

Fruiting summer. Dry rocks, gravel, sand, talus slopes, eskers, on limestone; 0-1000 m; Greenland; Alta., B.C., Man., Nfld. and Labr., N.W.T., Nunavut, Ont., Que., Sask., Yukon; Alaska; n Eurasia.