Ann. Lyceum Nat. Hist. New York 1: 71. 1824.
Plants cespitose; rhizomes very short or inconspicuous. Culms trigonous in cross-section, 10–105 cm, smooth distally. Leaves: basal sheaths dark reddish-brown; ligules longer than wide; blades mid to dark green, flat to W-shaped, widest leaves 3–10 mm wide, glabrous. Inflorescences 3–20 (–35) cm; proximal bract 19–70 (–100) cm, (2.5–) 3–9 times longer than inflorescence; proximal (2–) 3–6 spikes pistillate, ascending to spreading, at least the distal erect, ca. 20–150-flowered, cylindric; terminal 1 (–3) spikes staminate, slightly if at all elevated beyond summit of crowded pistillate spikes. Pistillate scales narrowly ovate, 2.4–4.5 × 1.1–1.8 mm, shorter than perigynia, margins entire, apex acute to acuminate, awnless. Perigynia mostly reflexed at maturity, often green or straw colored, strongly 6–13-veined, veins running into beak, ovate, 6–10 × (1.6–) 2.1–3.4 mm, apex abruptly tapered; beak 2.1–4.5 mm, bidentulate, smooth, teeth straight, 0.3–1.1 mm. Stigmas 3. Achenes pale-brown, symmetric, not indented, trigonous, smooth.
Phenology: Fruiting Jun–Aug.
Habitat: Swamps, wet thickets, often along streams, marshes, sedge meadows, shores of streams, ponds, and lakes
Elevation: 0–1900 m
B.C., Man., N.B., Ont., Que., Sask., Conn., Idaho, Ill., Ind., Iowa, Maine, Mass., Mich., Minn., Mont., N.Y., Oreg., Pa., Utah, Vt., Wash., Wis., Wyo.
Very rarely, specimens appear to be intermediate between Carex retrorsa and C. lupulina or C. lupuliformis; they are likely hybrids.