Enum. Pl. 2: 234. 1805.
Plants perennial, cespitose, 80–150 cm; rhizomes absent. Culms excurvednodding, leafy, triangular, slender; principal leaves overtopped by culm; blades flat, 2.5–5 mm wide, apex attenuate, trigonous. Inflorescences terminal and axillary, spikelet clusters mostly 2–6, compact, turbinate to hemispheric, 1.5–2 cm wide; peduncles progressively shorter distally on culm; bracteal leaves mostly exceeding subtended groups. Spikelets crowded, deep redbrown, lanceellipsoid, 4.5–6.5 mm; fertile scales ovatelanceolate, 3.5–4(–4.5) mm, apex acute, midrib mostly shortexcurrent. Flowers: perianth bristles 6, overtopping tubercle, antrorsely barbellate. Fruits (1–)2(–3) per spikelet, 3–4 mm; body dark redbrown with pale center, stipitate, lenticular, obovoid, or orbicular, 1.5–2 × 1.2–1.4 mm, base narrowed, margins pale, wirelike; surfaces slick; tubercle triangular-subulate, 1.3–1.5(–1.8) mm.
Phenology: Fruiting summer–fall.
Habitat: Moist to wet meadows, swales, fens, flatwoods, and bogs, 0–500 m
Ala., Ark., Del., Fla., Ga., Ill., Ky., La., Md., Miss., N.J., N.C., Okla., S.C., Tenn., Tex., Va., W.Va.
Rhynchospora glomerata is often associated with R. capitellata and is distinguishable by its taller, slightly stouter habit; longer, slightly paler spikelets; and longer and broader fruit body. It is a common lowland weed in the southern Piedmont, Atlantic coastal plain, and Gulf coastal plain, where it is often more associated with R. inexpansa.