Culms phyllopodic, with dead leaf remains at base, 20–60 cm. Leaf blades 1.5–4 mm wide, margins sometimes revolute, scabrid at tip. Inflorescences: proximal bracts 0.5-2 cm, shorter than inflorescences; lateral spikes 12–20 × 6–8 mm, with (7–)10–25 perigynia; terminal spikes 10–25 × 2.2–3 mm. Pistillate scales ovate-circular, 3.5–4.5 × 2.1–3.8 mm, slightly shorter than and wider than perigynia, apex acute to acuminate, mucronate, or shortly awned less than 1.5 mm. Staminate scales oblong-ovate, 3–4.7 × 1.2–2.4 mm, apex obtuse. Anthers 2–2.3 mm. Perigynia 3.2–4.2 × 1.5–2.6 mm, apex tapering to rounded; beak absent.

Fruiting summer. Bogs, marshes, stream banks, shores, sometimes brackish; 0–1000 m; B.C.; Alaska, Wash.; ne Asia (e Russian Far East, Commander Islands).

The name Carex stygia has been incorrectly applied to specimens of C. pluriflora. T. V. Egorova (1999) treated C. pluriflora as a subspecies of C. rariflora.