Rhizomes coarse, 1.5-2.8 mm thick, typically with long, unbranched segments from which shoots arise singly every few nodes. Culms sharply trigonous, (10-)20-80 cm, scabrous-angled distally. Leaves: basal sheaths dark brown; sheaths with hyaline inner band, apex prolonged 0.3-1.6 mm beyond base of blade, glabrous; ligules 0.6-2.7 mm; blades 1-3.7 mm wide. Inflorescences dense to elongate, 1-3 cm; spikes 4-12(-18), usually unisexual; staminate spikes lanceoloid; pistillate spikes ovoid. Pistillate scales reddish brown to dark brown, with narrow hyaline margins, ovate, apex acute to acuminate-awned, shiny. Anthers 1.8-3.1 mm, apiculus smooth to warty (30X). Perigynia dark reddish brown, essentially veinless, stipitate, broadly ovate to rhombic-orbicular, thickly plano-convex, 1.8-2.8 × 1.1-1.7 mm, shiny; beak 0.25-0.5 mm, hyaline, oblique or obscurely bidentulate.

Fruiting Jun-Aug. Wet meadows, marshes, seeps, fens, bogs, stream banks, lakeshores, ditches, tolerant of alkaline soils; 600-3100 m; Alta., Sask.; Ariz., Calif., Colo., Idaho, Mont., N.Mex., Oreg., Utah, Wash., Wyo.