Cas. Nár. Mus., Odd. Prír. 140: 127. 1972.
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 orangebrown or flanks red, central region usually greenish, aging brown, ovatelanceolate, 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, compressedtrigonous, 3–4.5 × 1.7–2 mm; beak 0.7–2 mm.
Phenology: Fruiting late spring–summer.
Habitat: Emergent (to submerged), in fresh to slightly brackish ponds and marshes, spring-fed streams, mainly on coastal plains
Elevation: 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).
"prolonged" is not a number.