Allg. Bot. Z. Syst. 17(Beil.): 3. 1912.
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 orangebrown or central region greenish, ovatelanceolate, 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.
Phenology: Fruiting summer.
Habitat: Emergent in fresh ponds and marshes, often with fluctuating water levels
Elevation: 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)].
"prolonged" is not a number.