Plants densely cespitose. Culms 23-56 cm. Leaves: sheath adaxially white-hyaline, summits U-shaped to rounded, often prolonged to 6 mm beyond collar; distal ligules 0.8-2.5(-4) mm; blades (2-)3-4 per fertile culm, 6-30 cm × 1.7-3.6 mm. Inflorescences dense or open, green and brown, gold, or brown, 1.4-3 cm × (5-)8-15 mm, stiff, appearing coarse-textured; proximal internode 3-7 mm; 2d internode 1-4 mm; proximal bracts usually aristate, shorter than inflorescences. Spikes 3-7, distant to loosely aggregated, usually individually distinct, narrowly to broadly ovoid, 7-10 × (3-)4.5-7.5 mm, base rounded or attenuate, apex usually acute. Pistillate scales white, gold, red-brown, or chestnut-brown, usually with pale to green midstripe, ovate to broadly ovate, 2.8-3.7 mm, shorter or longer and narrower than perigynia, margin occasionally white, 0.1-0.2(-0.5) mm wide, apex usually acute to acuminate. Perigynia appressed-ascending to ascending-spreading, green or gold, usually green toward beak, contrasting in color with pistillate scales, conspicuously 0-7-veined abaxially, conspicuously 0(-5)-veined adaxially, thin, ovate to broadly ovate, plano-convex or, more often, biconvex, (3.3-)3.5-4.3 × (1.3-)1.5-2 mm, 0.5-0.6(-0.8) mm thick, 2.1-2.7 times as long as wide, margin flat, including wing 0.2-0.4 mm wide, ciliate-serrulate at least on distal body, without metallic sheen; beak gold, gold-brown, red-brown, or brown at tip, flat, ± ciliate-serrulate or cylindric, unwinged, ± entire for 0.6 mm, abaxial suture usually inconspicuous, distance from beak tip to achene 1-2.4 mm. Achenes broadly oblong, ovate, broadly elliptic, or quadrate, 1.5-2 × 1-1.5 mm, 0.4-0.7 mm thick. 2n = 80.

Fruiting summer. Open dry to seasonally dry areas; 1000-3400 m; Alta., B.C., Yukon; Alaska, Calif., Idaho, Mont., Oreg., Wash.

Carex preslii has been synonymized with C. pachystachya (A. Cronquist 1969; C. L. Hitchcock and A. Cronquist 1973; A. Cronquist et al. 1972+).