Rhizome long; shoots ± loosely tufted. Culms erect, triquetrous, scabrous, 10–90 cm long, c. 1 mm diam. Leaves exceeding culms, 2–4 mm wide, dark green, margins antrorsely scabrous; sheath pale yellow-brown to orange-brown; ligule acute. Inflorescence erect, 7–18 cm long, with 3–8 spikes solitary at nodes; lowest involucral bract shorter than inflorescence. Spikes sessile to subsessile, distant, erect to spreading at maturity; upper 1 or 2 spikes male, 2.5–6.5 cm long; lower spikes female or often male at apex or base, 1.5–6.5 cm long; glumes often shortly mucronate, very dark red-brown with paler midrib, or rarely male glumes mostly stramineous; male glumes subacute to acute, occasionally obtuse; female glumes obtuse to acute, 2.8-.5 mm long; utricles 2.7–4.5 mm long, 1.5–2.0 mm diam., ovoid to ellipsoid, numerous-nerved, minutely papillose at least near apex, pale green to brown, often red-dotted; beak c. 0.3 mm long, with apex notched to truncate and occasionally minutely hispid; style 2-fid, or occasionally 3-fid in a few flowers within an inflorescence. Nut globose to obovoid, lenticular, dark yellow-brown. Flowers spring–summer.