Amer. J. Sci. Arts 14: 351, plate Q, figs. 53, 54. 1828.
Culms 12–80 cm. Leaves 2–6 per culm; sheaths tight, inner band hyaline, 3.5–21 cm, apex concave, glabrous; ligules rounded, 0.8–1.8 × 0.6–1.6 mm; blades involute, 4–70 cm × 0.4–1.5 mm, widest leaf 0.8–1.5 mm wide. Inflorescences 0.6–4 cm; spike 1 (occasionally 1–3 smaller accessory spikes), gynecandrous with staminate portion of spike 1–3 mm wide, to 50-flowered and pistillate portion of spike 5–9.5 mm wide, to 27-flowered or plants sometimes unisexual with staminate and pistillate spikes on different plants. Pistillate scales ovate, 1.8–3.3 × 1.3–2.2 mm, apex acute. Staminate scales lanceolate to ovate, 1.7–5.5 × 1–2.2 mm, apex acute. Anthers (2–)2.2–3.6 mm. Perigynia spreading to reflexed, castaneous to dark brown, 15-veined abaxially, faintly 7-veined adaxially, lanceolate-ovate to broadly ovate, 2.6–4.7 × 1.25–2.3 mm, 1.3–2.65 times as long as wide; beak 0.5–1.7 mm, 0.2–0.65 length of body, serrulate, teeth blunt, to 0.35 mm, soft. Achenes ovate, 1.4–2.2 × 1.2–1.7 mm.
Phenology: Fruiting late spring–early summer.
Habitat: Fens, bogs
Elevation: 0–500 m
St. Pierre and Miquelon, N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que., Ala., Del., Maine, Md., Mass., Mich., Minn., Miss., N.H., N.J., N.Y., N.C., R.I., Vt., Wis.