Plants perennial, cespitose, 30-100 cm; rhizomes absent. Culms erect to ascending-arching, slender, nearly terete, multiribbed. Principal leaves exceeded by culm; blades flat, linear, 1-2 mm wide, apex tapering, trigonous. Inflorescences: spikelet clusters 3-7, widely spaced, clusters loosely turbinate to hemispheric, to 1.3 cm wide. Spikelets brown to pale red-brown, lance-fusiform, 3-5.5 mm; fertile scales elliptic, 2.5-4 mm, acute, midrib short-excurrent. Flowers: perianth bristles 6, ± equaling tubercle. Fruits 1 per spikelet, (2.5-)2.7-3.3(-3.5) mm, body pale brown with yellowish center, ± broadly oblong-obovoid distal to stipe, lenticular, 1.5-2 × 0.8-1 mm; tubercle narrowly triangular subulate, (1-)1.2-1.5(-2) mm, less than 0.5 mm wide at base. Fruiting summer-fall. Moist sands and sandy peats of savannas, acidic stream banks, seeps, flatwoods, ditches, and pond shores; 0-400 m; Ala., Del., D.C., Fla., Ga., La., Md., Miss., N.J., N.C., Okla., S.C., Tenn., Tex., Va. Some specimens of Rhynchospora chalarocephala are very difficult to distinguish from R. microcephala, and unquestionably intergrades occur in peninsular Florida and the Gulf southern coastal plain. Rhynchospora chalarocephala tends to have longer, paler, narrower spikelets in looser clusters; the dilated part of the fruit body has a narrower, more oblong outline; and the tubercle is both narrower with a narrower base and longer (mostly 1-1.5 mm versus 0.9-1.2 mm in R. micro-cephala). Most material is easily sorted because R. chalarocephala has paler spikelets in turbinate to hemispheric clusters; the dark brown spikelets of R. microcephala are in globose heads.
Much like the more slender and narrow-lvd forms of no. 8 [Rhynchospora cephalantha A. Gray], but the glomerules hemispheric to broadly turbinate (the lower spikelets ascending or merely spreading), mostly 8-15 mm thick; achenes 1.4-1.8 mm, half to three-fifths as wide, the basal stipe-like part longer than in no. 8 [Rhynchospora cephalantha A. Gray]. Acid swamps and bogs on the coastal plain; N.J. to Fla.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.