Contr. U. S. Natl. Herb. 11: 172. 1906.
Plants densely cespitose. Culms (5–)15–45 cm. Leaves: sheaths adaxially white-hyaline, summits U-shaped or rounded, often prolonged to 2.5(–3) mm beyond collar; distal ligules 1.5–2.5(–3) mm; blades 3–5 per fertile culm, often channeled, occasionally folded, becoming trigonous toward tip, 5–20 cm × 1–2.5(–3) mm, if not folded, margins revolute. Inflorescences usually dense, stiff, gold to brown or brown and green, 1.5–3.5(–4) cm × 10–15 mm; proximal internode 4–10 mm; 2d internode 2–5 mm; proximal bracts scalelike to bristlelike, shorter than inflorescences. Spikes (3–)4–7, distant, distinct, ovoid to broadly ovoid, 12–15 × 5.5–8 mm, base rounded to attenuate, apex acute to truncate. Pistillate scales gold or brown, usually with pale to green midstripe, lanceolate to ovate, 3.7–5.1 mm, usually ± equaling and covering perigynia, margin white-hyaline, 0.1–0.3 mm wide, apex acute to acuminate. Anthers early deciduous or short-persistent. Perigynia ascending, greenish or pale gold to brown, conspicuously (0–)4–9-veined abaxially, conspicuously 0(–4)-veined adaxially, narrowly ovate to broadly ovate, flat or plano-convex, 3.8–5.2 × 1.5–2.3 mm, 0.4–0.5 mm thick, margin flat, including wing 0.3–0.5 mm wide, ciliate-serulate at least on distal body, not crinkled, without glossy metallic sheen; beak brown to red-brown or gold with white-hyaline tip, cylindric, unwinged, ± entire for 0.6 mm, abaxial suture with conspicuous white margin, distance from beak tip to achene 1.8–2.2 mm. Achenes ovate to broadly ovate or, occasionally, elliptic, 1.5–2 × 0.8–1.1(–1.2) mm, 0.3–0.5 mm thick. 2n = 84.
Phenology: Fruiting summer.
Habitat: High-montane to alpine areas, usually rocky soils
Elevation: 1200–4000 m
Alta., B.C., Alaska, Calif., Colo., Idaho, Mont., Nev., Oreg., Utah, Wash., Wyo.
Reports of Carex phaeocephala from northern Canada are based on other species, mostly C. tahoensis.