Plants perennial, not cespitose, long-creeping rhizomatous. Culms 10-35(-50) cm, smooth. Leaves flat, 10-30 cm × 1-3.5 mm. Inflorescences: spike 1, ovoid, 7-12 × 6-10 mm; bracts 3-4, horizontal to slightly reflexed, flat, 2-20(-30) cm × 1-3 mm. Spikelets 40-80, pale greenish or reddish brown, ovate, 3.5-4.5 × 1.2-1.3(-1.4) mm; floral scales laterally 2(-5)-veined, elliptic, 1.8-3.2 × 1-1.6 mm, apex mucronate; stamens 2-3; anthers 0.8-1.1 mm; style 1.8-2.2 mm; stigmas 0.5-1 mm. Achenes brown, sessile or stipitate, broadly ellipsoid, 1.5-1.8 × 0.8-1 mm, stipe, if present, to 0.1 mm, apex obtuse, apiculate, puncticulate. Fruiting summer. Muddy banks of streams and estuaries; 0-1000 m; introduced; Ala., Ark., Conn., Del., Ga., Ky., Md., Miss., N.J., N.Y., N.C., Pa., Tenn., Va.; temperate e Asia.