Sida 4: 119, fig. 38. 1971.
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 redbrown, ovoid to lanceoloid, 5–6 mm; fertile scales broadly ovate, 1.5–2 mm, acute to obtuse-angled, midrib shortexcurrent as mucro. Flowers: stamens 1–2; styles 2-fid, flat, fimbriate. Achenes whitened-iridescent to brown, lenticular or pyriformobovoid, 1 mm, cancellate, each face with 5–12 vertical rows of transversely oriented rectangular pits, achene margins distally papillose. 2n = 20.
Phenology: Fruiting late summer–fall.
Habitat: Disturbed sites, low pinelands, banks, and fields
Elevation: 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.