Plants perennial; cespitose, not rhizomatous. Culms (40)100-200(250) cm. Sheaths shiny and indurate basally, glabrous or appressed hairy elsewhere, hairs to 5 mm; ligules 0.2-0.7 mm; blades (10)25-50 cm long, (2)3-10 mm wide, flat to folded, pale bluish-green, yellowing at maturity, glabrous on both surfaces or the adaxial surface sparsely hairy basally, margins scabridulous. Panicles (18)30-50 cm long, 4-15 cm wide, open (contracted when immature), longer than wide, not diffuse, pyramidal to ovate; lower nodes with 1-2(3) branches; primary branches 4-15 cm, spreading 10-90° from the rachis, not capillary, without spikelets on the lower 1/3; secondary branches spreading; pulvini hairy or glabrous; pedicels 2-14 mm, longer than the spikelets, spreading, glabrous, sometimes scabridulous. Spikelets (3.7)4-6 mm, purplish-brown. Glumes linear-lanceolate, membranous; lower glumes 2.5-5.1 mm, (0.6)0.75-0.9(0.94) times as long as the upper glumes; upper glumes 3.7-5.7 mm, longer than the florets; lemmas 3-4 mm, ovate to lanceolate, membranous, glabrous, acute; paleas 3-4 mm, ovate, membranous, glabrous; anthers 2-3.1 mm, purplish. Fruits 1.7-2 mm, fusiform, reddish-brown. 2n = unknown.

Sporobolus floridanus grows in wet to mesic pine woodlands, seepage bogs, and treeless swales, in soils semi-permanently to seasonally saturated at the surface, and in places where water may pond for weeks, at elevations of 0-100 m. It is endemic to the southeastern United States.