Plants perennial, cespitose, to 100 cm; rhizomes sometimes produced, short, not stoloniferous. Culms lax, erect to ascending-excurved, ± terete, leafy, slender, soft. Leaves exceeded by inflorescence; blades erect or ascending, linear, proximally flat, 2-4 mm wide, apex trigonous, subulate, tapering. Inflorescences: spikelet clusters 4-6, widely spaced, loose, broadly to narrowly turbinate, paniculate, branches capillary, ultimate branches with 1 or 2 spikelets; leafy bracts exceeding proximal clusters, setaceous. Spikelets solitary or in 2s, brown, ovoid, 2.5-3.5 mm; fertile scales ovate, 1.5-2.2 mm, apex acute, apiculate. Flowers: perianth bristles 6, reaching tubercle base or slightly beyond, antrorsely barbellate. Fruits 2-3 per spikelet, 1.5-1.6(-1.8) mm; body brown or greenish, obovoid, lenticular, 1.1-1.2(-1.3) × 0.7-1 mm, margins narrow, distinct, sharp, flowing to tubercle; surfaces finely transversely wavy rugulose, intervals of fine, nearly isodiametric or vertical-rectangular pitlike alveolae; tubercle low triangular, entire, 0.3-0.4 mm.

Fruiting late spring-summer. Sandy alluvium of swamp forests and environs; 0-100 m; Ala., Fla., Ga., La., Miss., N.C., S.C.

Rhynchospora decurrens superficially resembles R. mixta, with which it is often associated in swamp forests. Its narrower fruit bodies with less distinct transverse rugosity; the smaller, more numerous rows of finer, pitlike alveolae; and its broader, lower tubercles with non-setose edges all comprise consistent differences. The name decurrens is apt, calling attention to the narrow, wirelike pale margins that extend from tubercle base to near the base of the fruit body.