Plants mat-forming; rhizomes 1-3 mm diam. Culms sharply trigonous, sides concave distally, 0.4-1.5 m × 1.5-5 mm. Leaves 4-7, nearly equaling culm; sheath fronts delicately pinnate-fibrillose; blades 3-6, erect, the distal mostly longer than sheath, 1-2 mm, wide, proximally thickly V-shaped central region trigonous-channeled to laterally flattened, apically asymmetically laterally flattened-trigonous; apex often markedly eccentric, glabrous, smooth or angles papillose. Inflorescences capitate or 1 spikelet; proximal bract erect, resembling leaf blade, 3-20 cm. Spikelets 1-4, 7-18 × 3-5 mm; scales straw-colored to orange-brown or central region greenish, ovate-lanceolate, 4-5 × 2.5 mm, margins entire, smooth or awn sparsely spinulose, sometimes distally ciliolate at 40X, apex acute, mucronate, mucro 0.2-0.5 mm. Flowers: perianth members 6, brown, bristlelike, equaling to slightly exceeding achene, spinulose; anthers 2-3 mm; styles 3-fid. Achenes brown, compressed trigonous, ovoid to obovoid, 3.5-4.5 × 1.7-2 mm; beak 0.5-1 mm. 2n = 70. Fruiting summer. Emergent in fresh ponds and marshes, often with fluctuating water levels; 10-200 m; Man., N.B., Ont., Que.; Conn., Del., Ill., Ind., Iowa, Ky., Maine, Mass., Mich., Minn., Mo., N.H., N.J., N.Y., Ohio, Pa., R.I., Vt., Va., Wis. Schoenoplectus torreyi is very locally distributed, and probably has been extirpated from many historic localities. A specimen from an uncertain locality in Kentucky was collected in 1830. I have not seen specimens from North Dakota, South Dakota, or Nebraska. Scirpus torreyi was placed in synonymy under S. subterminalis Torrey var. cylindricus (Torrey) T. Koyama [misapplied, = Bolboschoenus novae-angliae by T. Koyama (1962b)].