Plants loosely cespitose, long-rhizomatous. Culms 14-37 cm. Leaves: basal sheaths dark reddish brown; blades mostly basal, pale green, shorter than culms, thick, 1.7-4.5 mm wide. Inflorescences: peduncles of proximal spikes short; peduncles of terminal staminate spikes 1.5-3(-10) mm; proximal bracts short-sheathing; pistillate spikes 1-3, emerging from cauline nodes, aggregated, ascending, ovoid to short-cylindric; staminate spikes 8-22 × 1.8-3.1 mm. Scales: pistillate scales dark reddish brown, ovate to obovate, apex obtuse to acute, minutely ciliate; staminate scales dark reddish to purplish brown, ovate to obovate, margins white, apex acute, scarious. Anthers 1.9-3.1 mm. Perigynia ellipsoid to obovoid, 2.5-3 × 1.4-1.7 mm, base tapering, pubescent with straight white hairs; beak 0.5 mm. Stigmas 4, erect or convolute, thick, weakly papillose. Achenes obovoid, 1.9-2.5 × 1.3-1.6 mm.

Fruiting spring-summer (late Apr-late Jul). Moist to dry, open pine, spruce, Douglas-fir, and aspen woods, often on slopes; 60-2100 m; Alta., B.C.; Calif., Idaho, Mont., Oreg., Wash.

Carex cocinnoides is the only North American sedge with four stigmas per pistil. It is most similar to C. richardsonii; differs in its more closely aggregated, short-pedunculate pistillate spikes with very short-sheathing bracts. These close relatives are sympatric only at the northern and eastern edge of the range of C. concinnoides.