Herbs, perennial, cespitose, with well-developed rhizomes. Culms trigonous, 30-100 cm × 2-4 mm, basally cormlike, glabrous. Leaves flat to broadly V-shaped, 20-70 cm × 4-6 mm, glabrous except for marginal prickles. Inflorescences: spikes loosely to densely ovoid, oblong (2 times long as wide), 10-12 × 6-9 mm; rays 6-11, 1-16 cm, glabrous; bracts 5-10, ascending at 30-45°, flat, 6-25 cm × 3-6 mm; rachilla persistent, wings 0.5 mm wide, covering nearly entire length of achene. Spikelets (20-)40-100(-120), proximal spikelets reflexed somewhat, distal ones divaricate, ± terete, lanceoloid, 6-6.8 × 1-1.4 mm; floral scales persistent, 1-2(-3), appressed, golden brown, lanceolate, laterally 5-6-ribbed, 3.8-4.9 × 1.4-1.6 mm, apex mucronate, mucro at most 0.3 mm. Flowers: anthers 1-1.3 mm; styles 0.8-1 mm; stigmas 2-3 mm. Achenes brown, sessile, linear, 2.5-2.8 × 0.5-0.7 mm, apex obtuse, apiculate, surfaces muriculate. Fruiting late summer-early fall (Jul-Sep). Xeric, sandy soils of sand hills and pine barrens; 0-200 m; Ala., Ark., Del., D.C., Ga., La., Md., Miss., Mo., N.J., N.C., Tex., Va. Cyperus hystricinus resembles C. plukenetii and C. retrofractus; it can be readily distinguished from both by its glabrous culms. Overly mature specimens of C. lancastriensis are frequently misidentified as C. hystricinus; C. hystricinus may be confirmed by its narrow, nearly glabrous leaves and bracts, golden brown spikelets, longer, narrower achenes, and elongated rhizome internodes (to 15 mm vs. 5 mm in 76. C. lancastriensis).
Much like no. 18 [Cyperus retrofractus (L.) Torr.], but smooth except for a few remote marginal teeth on the lvs; spikes golden-brown at maturity, twice as long as thick; scales lanceolate; rachilla- wings clasping the achene for its whole length. Dry, sandy places; N.J. to n. Fla. and e. Tex., especially on the coastal plain. (C. retrofractus var. h.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.