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.).