Herbs, perennial, cespitose; rhizomes upright, 5-8 mm diam., indurate. Culms trigonous, 30-50(-80) cm × 1.8-2.5 mm, glabrous. Leaves 4-7(-10), V-shaped, (20-)40-60 cm × 4.5-8 mm. Inflorescences: heads dense, hemispheric, 7-15(-18) mm diam; or if rays absent, heads dense, irregularly lobate, 2-3.5 cm diam.; rays 3-6, 1-30 mm; 2d order rays infrequently present, to 5 mm; bracts (5-)10-15(-40), horizontal to ascending at 30(-45)°, V-shaped, 6-30(-40) cm × 5-8(-10) mm. Spikelets 40-100, greenish white, flattened, ovoid, 3.5-5 × 3-4 mm; floral scales (8-)12-16, uniformly light greenish to light brown, laterally 1-ribbed, medially indistinctly 3-ribbed, basally 2-keeled, oblong-spatulate, widest at or above median, 2-2.5 × (0.7-)1-1.2 mm, apex minutely mucronate, scabridulous, infrequently glabrous. Flowers: stamen 1; anthers oblong, 0.7-1 mm, connective apex subulate, prolonged 0.1-0.2 mm; styles thick, confluent with apex of, and persistent on, achene, 0.5-0.8 mm; stigmas 0.6-1 mm. Achenes brown, stipitate, linear, slightly curved, 1.2-1.4 × 0.2(-0.3) mm, base whitish, stipe spongy, 0.1-0.2 × 0.2 mm, apex acute, surfaces papillose. Fruiting summer. Damp places; 0-200 m; Ala., Ark., Del., D.C., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Mass., Mo., N.J., N.C., Okla., S.C., Tenn., Tex., Va. Cyperus pseudovegetus is introduced in Massachusetts.