384. Carex retrorsa Schweinitz, 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.
Fruiting Jun–Aug. Swamps, wet thickets, often along streams, marshes, sedge meadows, shores of streams, ponds, and lakes; 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.