Plants annual, cespitose, to 30 cm, base soft, not bulbous; rhizomes absent. Leaves nearly distichous, mostly spreading, to 2/3 length of culms; sheaths ciliate, sheath backs often pilose-hirsute; ligule present, complete; blades narrowly linear, 1.5–2.5 mm wide, flat or shallowly concave, margins scabrid, abaxial surface scattered-pilose, hirsute-ciliate at least proximally. Inflorescences: anthelae simple or compound, open, divaricately branched, mostly as broad as long; scapes slender, 1 mm wide, distally slightly compressed; proximalmost involucral bract exceeding or shorter than anthela. Spikelets pale brown or red-brown, ovoid to lanceoloid, 5–6 mm; fertile scales broadly ovate, 1.5–2 mm, acute- to obtuse-angled, midrib short-excurrent as mucro. Flowers: stamens 1–2; styles 2-fid, flat, fimbriate. Achenes whitened-iridescent to brown, lenticular or pyriform-obovoid, 1 mm, cancellate, each face with 5–12 vertical rows of transversely oriented rectangular pits, achene margins distally papillose. 2n = 20.

Fruiting late summer–fall. Disturbed sites, low pinelands, banks, and fields; 0–100 m; Ala., Fla., Ga., La., Miss., N.C., S.C., Tex.

In the Atlantic and Gulf Coastal plains, Fimbristylis decipiens often shares habitat with two close, likewise weedy, relatives: F. dichotoma and F. annua. From the former F. decipiens is distinguished by its annual habit, its papillose distal achene edges, and the more spreading anthela branches; from the latter it differs in its usually less papillose achene and its harder, more spreading foliage. No intergrades appear to occur among the three.