Plants mat-forming; rhizomes 1-3 mm diam. Culms proximally bluntly and distally sharply trigonous, 0.6-2 m × 3-5 mm. Leaves 5-20+, nearly equaling culm; sheath fronts delicately pinnate-fibrillose; blades 2-6+, smooth; distal blade longer than sheath, 2-10 mm wide, smooth; emergent blades stiff, cross section thickly V-shaped to trigonous near ligule, central region acutely trigonous and laterally flattened, distal region laterally flattened, apex often asymmetric; submerged blades often flaccid, ribbonlike. Inflorescences 2-3 times branched, 2-3 proximal internodes elongated, branches to 16 cm; proximal bract erect, resembling emergent leaf blade, 7-32 cm. Spikelets 3-20, 10-25 × 5-6 mm; scales straw-colored to orange-brown or flanks red, central region usually greenish, aging brown, ovate-lanceolate, 5-7 × 3 mm, smooth, margins sometimes ciliolate at 40X, apex acute, entire, mucro to 0.2 mm. Flowers: perianth bristles 6, medium brown to reddish, equaling achene, sparsely spinulose; anthers 3-3.5 mm; styles 3-fid. Achenes medium brown, ovoid to obovoid, compressed-trigonous, 3-4.5 × 1.7-2 mm; beak 0.7-2 mm.
Fruiting late spring-summer. Emergent (to submerged), in fresh to slightly brackish ponds and marshes, spring-fed streams, mainly on coastal plains; 10-100 m; Ala., Del., Fla., Ga., La., Md., Miss., Mo., N.C., R.I., S.C., Tex., Va.
Scirpus etuberculatus was placed in Scirpus sect. Bolboschoenus by T. Koyama (1958) and G. C. Tucker (1987).
Perennial from stout rhizomes; stems erect, sharply triangular, 1-2 m, nearly or quite equaled by the 2-3 elongate, channeled and keeled aerial lvs; submerged, ribbon-like lvs usually present; primary bract erect, 1-2 dm, the primary peduncles either elongate with solitary spikelets or short and producing a secondary bract up to 1 dm with other peduncled spikelets; spikelets narrowly obovoid, 1-2 cm; scales lance-ovate, 6 mm, acuminate or acute and mucronulate; achene obovoid, trigonous, nearly black, the body 2.5-3 mm, conspicuously (ca 1 mm) apiculate; bristles 6, 4 mm. Swamps and quiet or flowing shallow water on the coastal plain; Del. to Fla. and Tex., n. to s. Mo. Fr June-Aug. (Schoenoplectus e.)
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.