Proc. Amer. Acad. Arts 7: 394. 1868.
Plants densely cespitose. Culms reddish brown to dark maroon at base; flowering stems 20–70 cm, much longer than leaves at maturity, 1–1.7 mm thick, glabrous or sparsely pilose. Leaves: basal sheaths reddish brown, bladeless, pilose; others grading from dark red to green on back, tan-hyaline on front, reddish brown dotted and usually pubescent at apex; blades flat, 3–12 mm wide, usually pilose, more densely so abaxially, margins ciliate. Inflorescences: peduncles of lateral spikes, when present, less than 10 mm, often pubescent; proximal bracts usually shorter than inflorescence; sheaths 5–50 mm; blades 1.2–2 mm wide. Lateral spikes 2–5, 1 per node, usually crowded toward apex and overlapping staminate spike, erect, sessile or pedunculate, pistillate with 20–40 perigynia attached less than 1 mm apart, cylindric, 12–40 × 4–11 mm. Terminal spike staminate, rarely gynecandrous, sessile or very short-pedunculate, 8–30 × 2–5.5 mm. Pistillate scales reddish brown with narrow white-hyaline margins and green midrib, broadly ovate, shorter than mature perigynia, apex obtuse to short-cuspidate, often pubescent on midrib and awn, ciliate distally. Perigynia pale green, blotched with dark maroon at base, dark maroon-brown distally, 2-ribbed and finely veined with to 20 veins, most conspicuous near base, loosely enveloping achene, ellipsoid, 3.7–5.3 × 1–2.2 mm, membranous, base acute, apex narrowing to beak, body covered with long, appressed to spreading hairs; beak bidentate, 1 mm. Achenes substipitate, 2–2.6 × 1.2–1.7 mm. 2n = 50, 52.
Phenology: Fruiting late spring–early summer.
Habitat: Seeps, stream banks, roadside ditches, wet meadows and slopes, coastal prairies, mixed evergreen forest along the Pacific Coast
Elevation: 0–600 m
Sporadic sterile hybrids between Carex gynodynama and C. mendocinensis are well documented. A reported hybrid with C. hendersonii needs further study to confirm parentage.