Scirpus polyphyllus Vahl

Scirpus polyphyllus occasionally hybridizes with S. atrovirens.

Plants cespitose; rhizomes short, tough, fibrous. Culms: fertile ones erect or reclining; nodes sometimes with axillary bulblets. Leaves 14–22(–26) per culm; sheaths of proximal leaves green or brownish; proximal sheaths and blades with septa usually few, inconspicuous; blades 16–31 cm × 5–8 mm. Inflorescences terminal, rarely also with 1 lateral inflorescence from distal leaf axil; rays divaricate, smooth throughout or scabrous distally, rays usually with axillary bulblets; bases of involucral bracts green, not glutinous. Spikelets in dense clusters of 3–9 (largest cluster with 6 or more), spikelets sessile, broadly ovoid, 2.5–4 × 1.6–3 mm; scales reddish brown with green midribs, circular or nearly so, 1–1.5 mm, apex mucronate or occasionally short-awned, mucro or awn 0.2–0.3 mm. Flowers: perianth bristles persistent, 6, stout, contorted, much longer than achene and projecting beyond it, retrorsely barbed in distal 1/2, exserted from scales at maturity; styles 3-fid. Achenes pale brown, obovate or nearly obtriangular in outline, plumply trigonous or plano-convex, 1.1–1.4(–1.8) × 0.8–1 mm. 2n = 58.

Ala., Ark., Conn., D.C., Ga., Ill., Ind., Ky., Md., Mass., Miss., Mo., N.H., N.J., N.Y., N.C., Ohio, Pa., S.C., Tenn., Vt., Va., W.Va.

Fruiting summer (Jul–Aug).

Along wooded streams and other swampy places, usually shaded by trees; 0–1000m.

Scirpus polyphyllus Vahl, Enum. 2: 274. 1805
Scirpus exallatus Pursh, Fl. Am. Sept. 56. 1814.
Scirpus exallatus @ viviparus Pursh, Fl. Am. Sept. 56. 1814.
Scirpus brunneus Muhl. Descr. Gram. 42. 1817.
Scirpus brunneus /3 viviparus Torr. Ann. Lye. N. Y. 3: 327. 1836.
Scirpus brunneus y crispus Torr. Ann. Lye. N. Y. 3: 327. 1836.
Holoschoenus brunneus Steud. Nom. Bot. ed. 2, 1: 773. 1840.
Perennial; roots spongy, the rootstocks short; culms single at the nodes, usually ca. 6 dm. tall, to 1 m., triangular, green, smooth; sheaths green, drying brown, the blades to 3 dm. long, to 7 mm. broad, scabrous on the margins and midrib, tapered to a blunt tip; involucral bracts 3-5, leaflike, unequal, the primary rays of the umbel to 10 dm. long, smooth, the small heads of 3-15 spikelets on the shorter secondary rays; spikelets yellow-brown or reddish, ovoid, 2.5-3 mm. long; scales 1-1.5 mm. long, rounded, mucronate; bristles 6, usually twice bent, about twice the length of the achene; style trifid, dark red; achene ca. 1 mm. long, light brown, broadly obovoid, mucronate.
Type locality: "In America boreali?"
Distribution: Swamps and borders of ponds; Maine, south to Georgia, west to Indiana and Kentucky.