Plants annual, cespitose, (20-)30-80(-100) cm; rhizomes absent. Culms erect or ascending, leafy, nearly terete or obscurely angular, many-ribbed, stiff. Leaves exceeding or exceeded by inflorescences; blades linear, proximally flat, 1-5 mm wide, apex trigonous, tapering. Inflorescences terminal and axillary, clusters of corymbs 1-5, diffuse, branches ascending to divaricate; leafy bracts much exceeding axillary corymbs. Spikelets red brown to dark brown, ovoid lanceoloid, 3-6(-7) mm, apex acute; fertile scales several, narrowly ovate, 2.5-3.5 mm, apex narrowly acute; midrib included or short excurrent. Flowers: perianth absent. Fruits 1.3-1.5 mm; body brown to blackish, tumidly lenticular, nearly orbicular, 0.6-1 × 0.6-1 mm, margins distinct, narrow, flowing into base of tubercle; tubercle flat, narrowly triangular, at least 0.5 mm high, base broadly 2-lobed, apex acuminate. Fruiting summer-fall or all year (south). Moist to wet sands or peats of banks of streams and ditches, pond and lakeshores, depressions in savannas, marshes, often in moist to wet disturbed areas; 0-200 m; Ala., Conn., Del., Fla., Ga., Ind., La., Md., Mass., Mich., Miss., N.J., N.Y., N.C., R.I., S.C., Tex., Va., Wis.; West Indies.
Tufted annual 1-6 dm; blades 1-3 mm wide; spikes ovoid to cylindric, 3-7 mm, loosely clustered at the ends of the stem and branches; scales numerous, thin, 1-nerved, ovate, acute, 3 mm, each subtending a perfect fl, perianth wanting; stamens 1 or 2; achenes 0.7-1 mm, rotund or a little wider than long, contracted to a short broad stipe, longitudinally finely striate and sometimes obscurely cross-rugulose, pale brown, becoming nearly black, with raised pale margins; tubercle flat, triangular-subulate, nearly or quite as long as the achene. Wet sandy soil; e. Mass. and R.I.; nw. Ind. and sw. Mich.; se. Va. to e. N.C. (Psilocarya s.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.