Cyperus acuminatus var. cyrtolepis (Torrey & Hooker) Kükenthal; C. cyrtolepis Torrey & Hooker; C. cyrtolepis var. denticarinatus (Britton) Britton; C. rufescens Torrey & Hooker var. denticarinatus Britton

Herbs, annual, cespitose. Culms roundly trigonous, (10–)20–30(–45) cm × 0.4–1.2 mm, distal 1/2 glabrous or infrequently scabridulous. Leaves 2–6(–8), V-shaped or flat, 8–12(–16) cm × 1–2(–4) mm. Inflorescences: heads hemispheric, 7–12(–15) mm diam.; rays 1–3(–5), 0.5–2 cm; bracts 3–6, longest erect to ascending, flat to V-shaped, (1.5–)3–12(–25) cm × 1–2.5(–3.5) mm. Spikelets (15–)25–50(–75), ovoid, compressed, 4–7 × 2–3 mm; floral scales 8–20(–35), laterally yellowish, yellowish green, or light reddish brown, medially light brown or greenish brown, 2-keeled, subtly 1-ribbed, ovate-lanceolate, 1–2 × 1–1.4 mm, apex acute, mucronate, straight to excurved, glabrous or sparsely scabridulous. Flowers: stamen 1; anthers 0.5 mm; styles 0.8–1.1 mm; stigmas 0.5 mm. Achenes brown, stipitate, broadly ellipsoid, abruptly contracted to base, 0.8–1.1 × 0.3–0.4 mm, stipe 0.1 mm, apex acute, tapering to slender beak formed of persistent style base, surfaces papillose.

Fruiting summer–fall (Jul–Oct). Wet, often sandy shores and damp, disturbed soils; 0–1500 m; Ala., Ariz., Ark., Calif., Colo., Ill., Ind., Iowa, Kans., Ky., La., Mich., Minn., Mo., Mont., Nebr., N.H. (introduced?), N.Y. (introduced?), N.C., N.Dak., Ohio, Okla., Oreg., Pa. (introduced?), S.Dak., Tenn., Tex., Utah, Va., Wash., Wyo.; Mexico (Coahuila, Tamaulipas).