Herbs, perennial, cespitose, rhizomatous. Culms trigonous, basally tuberous thickened, 15-40 cm × 1-2.5 mm, glabrous. Leaves flat to V-shaped, 10-30 cm × 1-2 mm. Inflorescences: spike 1, densely oblong to ellipsoid, 8-36 × 8-20 mm; rays 4-12, 10-20 cm; bracts 3-6, horizontal to ascending at 30°, V-shaped, 3-15 cm × (3-)4-5.8 mm; rachilla deciduous, wings 0.5-0.7 mm wide. Spikelets (5-)20-35(-60), linear to oblong, quadrangular; 4-12(-21) × 0.7-1.2 mm, base narrowed to 0.4-1 mm; floral scales persistent, 1-3(-5), appressed, laterally whitish to reddish brown, stramineous with reddish spots, medially green, laterally 3-6-ribbed (midrib distinctly scabrid at 30X), narrowly oblong to ovate, 2.6-4.8 × 1.6-2 mm; apex rounded to ± acute, entire, with mucro 0.3-0.5 mm; sterile terminal scale involute, 0.4-0.6 mm wide, uncinate; distal floral scales with cusp 0.6-1.9. Flowers: anthers 0.5-1.3 mm; styles 0.4-0.5 mm; stigmas 0.5-0.9 mm. Achenes light brown to reddish brown, sessile to slightly stipitate, narrowly ellipsoid, 1.8-2.4 × 0.6-0.8 mm, apex slightly apiculate, surfaces puncticulate.

Fruiting mid summer-early fall (Jul-Sep). Damp, disturbed soils, croplands; 0-1000 m; Tex.; Mexico.

Included previously in Cyperus retroflexus (or its synonym C. uniflorus), C. floribundus has a much narrower geographic range (southern Texas and northeastern Mexico) and differs in features of spikelet morphology (J. R. Carter and S. D. Jones 1997).