Herbs, perennial, cespitose, rhizomatous; stolons tuberiferous, 1–10 cm. Culms trigonous, 8–50 cm × 1–3 mm. Leaves flat or V-shaped, 10–40 cm × 2–5 mm. Inflorescences: heads digitate, 8–18 mm diam.; rays 4–9, 1–8 cm; 2d order rays 0.5–2 cm; bracts 3–5, ± horizontal, flat, 1–20 cm × 1–4 mm. Spikelets commonly proliferous, 2–6, linear to oblong, compressed, 3–24 × 2–2.5 mm; floral scales 3–20(–50), reddish brown, laterally 1–3-ribbed, ovate, 2–2.5 × 1.5–2 mm. Flowers: stamens 3; anthers 1.5 mm; styles 1 mm; stigmas 1.5 mm. Achenes reddish brown, sessile, obovoid, 0.8–1 × 0.4–0.5 mm, apex obtuse, scarcely apiculate, surfaces glabrous.

Fruiting summer. Emergent sandy, peaty, or gravelly shorelines; 0–600 m; N.B., N.S., Ont., Que.; Conn., Del., D.C., Ind., Maine., Md., Mass., N.H., N.Y., N.C., Pa., R.I., S.C., Tenn., Vt., Va.

The report of Cyperus dentatus from West Virginia (M. V. McGivney 1938) is erroneous; the cited specimen was from New Jersey (Gutenberg s.n. 1886, US) (M. Strong, pers. comm.).