Herbs, annual, cespitose. Culms trigonous, 1-35 cm × 0.5-1 mm, glabrous. Leaves flat, 5-20 cm × 1-2 mm. Inflorescences: heads ± digitate, 8-26 mm diam.; rays 1-6, 0.5-5 cm; bracts 3-4, ± horizontal, flat, 3-18 cm × 1-2 mm. Spikelets 6-25, ovoid to linear-lanceoloid, compressed, 4-15 × 1-2 mm; floral scales 8-28(-40), clear, laterally ribless, ovate, 1.4-1.6 × 0.8 mm, apex awned, awn excurved, 0.3-0.5 mm. Flowers: stamens 1-2; anthers 0.2 mm; styles 0.5 mm; stigmas 0.3 mm. Achenes dark brown to black, sessile, obovoid, 0.6 × 0.4 mm, apex obtuse, apiculate, surfaces minutely punctate.

Fruiting spring-summer. Disturbed, sandy soils; 0-50 m; introduced; Fla.; West Indies (introduced); Asia; Africa (including Madagascar); Indian Ocean Islands; Pacific Islands; Australia.

Cyperus pumilus is distinctive because it is our only distigmatic Cyperus with awned floral scales.

Cyperus hyalinus Vahl, a southeastern Asian and Australian species, has recently been collected in Miami-Dade County, Florida (Mears s.n., EIU, VSC). This is an aberrant species sometimes placed in the monotypic genus Queenslandiella as Q. hyalina (Vahl) F. Ballard; it differs from C. pumilus in having deciduous rachillae as well as deciduous floral scales.