Plants perennial or annual, single or cespitose, (10-)20-50 cm; rhizomes absent. Culms spreading to erect, leafy, obtusely triangular. Leaves often exceeding inflorescences; blades narrowly linear, proximally flat, 1-3 mm wide, apex trigonous, tapering. Inflorescences terminal and axillary, clusters of 1-5 corymbs; leafy bracts much exceeding corymbs. Spikelets few to several, on ascending, stiff, short-to-elongate branches, red-brown to brown, lanceoloid, (5-)6-10 mm, apex acuminate; fertile scales many, ovate, shallowly convex, 5 mm, apex acuminate; midrib short-excurrent or not. Flowers: perianth absent. Fruits 1.5 mm; body dark brown to black, tumidly lenticular, nearly orbicular, 0.8-0.9 × 0.6-0.7 mm, margins grooved, discontinuous with tubercle; surfaces transversely wavy rugose, ridges of contiguous rows of vertical, linear, raised cells; tubercle broad, low triangular, 0.2-0.3 mm, crustaceous, base capping fruit summit, raised at ends, apex short acuminate.

Fruiting all year. Moist to wet sandy peaty swales, pond shores, depressions in savannas, moist waste areas; 0-100[-1000] m; Fla.; Mexico; West Indies; Central America; South America; Africa.

Rhynchospora eximia is often found at elevations from near sea level to over 1000 m in the tropics.