Plants perennial, densely cespitose, knotty based, 20-40 cm; rhizomes absent. Culms filiform, leafy at base, wiry. Leaves ascending to erect; blades filiform, nearly terete, or channeled, sometimes compressed, nearly reaching distal inflorescence or much shorter, 0.2-0.3 mm thick, apex subulate. Inflorescences: spikelet clusters 2-6, simple or reduced to 1 spikelet, branches ascending to divaricate or reflexed; leafy bracts single per cluster, filiform, setaceous, with clusters appearing lateral to bracts. Spikelets pale red brown, ellipsoid lanceoloid, 5-6(-8) mm, apex acute to acuminate; fertile scales oblong elliptic, convex, acuminate, 3.5-5 mm, apex broadly acute, midrib forming apiculus. Flowers: perianth bristles 6, reaching to or slightly past tubercle base, increasingly plumose from middle to base. Fruits 1-3 per spikelet, (2.5-)2.7-3(-3.4) mm; body light brown to brown, ellipsoid obovoid, distally conspicuously necked, tumidly lenticular, 1.7-2.5 × 1.5-1.8 mm; surfaces smooth or minutely transversely rugulose; tubercle conic subulate, 0.5-0.7 mm, base flaring.

Fruiting spring-summer. Sands and peats of bogs, depressions in savannas, open pinelands, seeps; 0-200 m; Ala., Del., D.C., Fla., Ga., La., Miss., N.J., N.C., S.C., Tex., Va.; West Indies; Central America.

Rhynchospora oligantha is distinguished from other taxa of its complex mostly by the distinctive neck at the achene apex, a feature essentially absent in R. breviseta, its closest relative. Those two species have been heavily impacted by conversion of pine savannas to cropland or pine plantations; even with abandonment or clearing of such land, they are very slow to reoccupy the disturbed sites.

Densely cespitose perennial 1.5-4 dm; stems very slender, triquetrous, lfless or 1-lvd near the base; lvs setaceous, about equaling the stem; infl of (1)2-5 spikelets on 1-2(3) short branches, subtended by an erect bract resembling a continuation of the stem, one branch diverging at a right angle, the other 1 or 2 erect or arcuate; spikelets light brown, 4-7 mm, with 2-4 fls and 1-3 frs; bristles 6, a little shorter to a little longer than the achene, strongly plumose toward the base; achenes brown, plump, elliptic to obovate, 2-2.7 mm, constricted just below the top, transversely rugulose; tubercle conic, 0.3-0.6 mm. Pine-barren bogs; N.J. to Fla., Tex., W.I., and C. Amer

Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.

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