Cyperus brizaeus J. Presl & C. Presl; C. polystachyos var. leptostachyus Boeckeler; Pycreus polystachyos (Rottbøll) Palisot de Beauvois

Herbs, perennial (annual?), cespitose. Culms trigonous or ± terete, (3–)20–45(–70) cm × (0.8–) 1.2–2 mm, glabrous. Leaves (2–) 6–10(–16), flat to V-shaped, (2–) 10–30(–60) cm × 1–4 mm. Inflorescences: spike 1, loosely ovoid to densely turbinate, 12–40 × 10–25 mm; rachis 3–10 mm; rays 1–8(–12), 0.5–3(–6) cm; 2d order rays absent; if rays absent, inflorescence single dense cluster of spikelets, 12–40 mm diam.; bracts (3–)4–6(–7), horizontal to ascending at 45°, flanged V-shaped, (2–)5–15(–23) cm × 1–4 mm. Spikelets (5–)15–30(–40), spreading to appressed-ascending, linear-lanceoloid to linear, compressed, 8–18(–40) × (1–)1.3–1.6(–2) mm; floral scales (8–)12–25(–66), laterally stramineous to light brown, medially green, laterally ribless, medially 3–5-ribbed, oblong, (1.5–)1.8–2.4 × (1–)1.2–1.4 mm, apex acute to ± acute, mucronate. Flowers: stamens 2; anthers (0.4–)0.5–0.8 mm, connective not prolonged; styles 0.6–1(–1.4) mm; stigmas (1–)1.4–2 mm. Achenes light to dark brown, oblong, (0.8–)0.9–1.1(–1.2) × 0.4–0.5(–0.6) mm, base cuneate to ± stipelike, apex truncate, apiculate, surfaces punctate to minutely punctate with raised cells.

Fruiting summer–early fall. Shores, ditches, swales between dunes; 0–200 m; Ala., Del., D.C., Fla., Ga., Ky., La., Maine, Md., Mass., Miss., N.J., N.Y., N.C., Okla., Pa., S.C., Tex., Va., W.Va.; Mexico; Central America; South America; Asia; Africa.

Cyperus polystachyos is polymorphic. Adequate understanding of the infraspecific variations of C. polystachyos requires a worldwide examination, which is beyond the scope of this study. The segregates, C. fugax and C. filicinus, are recognized here; they have been usually accepted by recent workers (e.g., M. L. Fernald 1950; H. A. Gleason and A. Cronquist 1991).