Herbs, perennial, cespitose, rhizomatous. Culms trigonous to terete, 20-100 cm × 2-6 mm, soft (flattened in drying), glabrous, often flopping over and rooting at base of rays. Leaves: blades reduced to sheath. Inflorescences: rays 100-250, 5-16 cm; 2d order rays 0.5-5 cm; bracts 2-3, horizontal or reflexed, 4-12 cm × 1.5-4 mm. Spikelets 1-30, linear-lanceoloid, ellipsoid to narrowly ovoid, compressed-quadrangular, 6-17 × 1-1.5 mm; floral scales 5-12, reddish brown, 1-3-ribbed, 1.2-1.7 × 0.7-0.9 mm, apex mucronulate. Flowers: stamens 3; anthers 1-1.2 mm; styles 0.3 mm; stigmas 1-1.3 mm. Achenes brown, obovoid, 0.4 × 0.2 mm, base stipelike to nearly cuneate, apex obtuse, surfaces finely reticulate.

Fruiting summer. Pond shores, marshes; 0-200 m; introduced; Calif., Fla.; tropical e Africa.

Cyperus prolifer has long been cultivated in fish ponds and water gardens and has been reported under the name C. isocladus.