Herbs, perennial; rhizomes ± horizontal, to 12 cm × 0.8-1.2 mm. Culms ± terete to roundly trigonous, 3-25(-60) cm × 0.3-2 mm, glabrous. Leaves 1-3, V-shaped, 1-8(-15) cm × 1-2 mm. Inflorescences: spike 1, loosely ovoid, 7-14 × 8-20 mm; rays (0-)1-4, to 2(-3) cm; bracts 2-4, horizontal to ascending at 30(-45)°, V-shaped to flat, 1-8(-18) cm × 0.5-1.5(-2) mm. Spikelets 3-5(-14), oblong to linear-lanceoloid, 8-18 × 2-2.6(-3) mm; floral scales (6-)10-26(-32), laterally clear to light brown, sometimes with purplish margins, medially light brown, 2-keeled, laterally ribless, medially 2-3-ribbed, oblong to ovate, 1.9-2.2(-2.7) × 1.8-2.3 mm, apex obtuse. Flowers: stamens 3; anthers ellipsoid, 0.3-0.6 mm, connective not prolonged; styles 0.6-1 mm; stigmas 1-1.5 mm. Achenes brown, ± stipitate, obovoid to ovoid, 1-1.4 × 0.6-0.8 mm, apex truncate, apiculate, surfaces minutely punctate.

Fruiting late summer-fall. Emergent shorelines, ditches; 20 m; introduced; Ala., Ga., La., Miss.; Asia; Africa.

Cyperus sanguinolentus is the only rhizomatous, distigmatic Cyperus in the eastern United States. An early collection from Louisiana was described as C. louisianensis, supposedly endemic. Recent field work and morphometric studies convincingly showed it to be an introduction of the Asian C. sanguinolentus) (J. R. Carter and C. T. Bryson 2001.