Native from temperate to tropical North and South America.In the Hawaiian Islands,
Annuals with fibrous roots; culms tufted, capillary, 5-30 cm tall, 0.2-0.5 mm in diameter.
Leaves 1/3-1/4 the length of the culm, blades capillary, 2-10 cm long, 0.3-0.6 mm wide, inrolled, sparsely pubescent to glabrate; sheaths reddish brown, membranous, pilose on oblique margins of orifice.
Inflorescences open with 1-3 capillary rays up to 2 cm long or subcapitate; involucral bracts 2-3, filiform, shorter than to twice as long as the inflorescence; spikelets 2-7, narrowly ovoid to ellipsoid, 3-4 mm long, ca. 1.5 mm wide, apex acute; glumes dark reddish brown, membranous, ovate, ca. 1.5 mm long, ca. 1 mm wide, apex subacute or shallowly emarginate, finely puberulent to glabrate, the midnerve prominent, yellowish green, otherwise nerveless; style base depressed-conical or depressed-globose, small.
Achenes obovoid-deltoid, 0.8-1 mm long, transversely rugulose with several vertical rows of transversely oblong cells, apex rounded, the angles obtuse, the sides pale or yellowish brown.