Annual greenhead sedge

Cyperus densicaespitosus Mattfeld & Kükenthal; C. tenuifolius (Steudel) Dandy; Kyllinga tenuifolia Steudel

Herbs, annual, cespitose, not rhizomatous. Culms (5–)15–30(–55) cm, smooth. Leaves flat to V-shaped, 4–20(–30) cm × 1.5–3(–3.6) mm. Inflorescences: spikes 1–3, pale greenish, (3–)5–8(–11) × 5–7 mm; bracts (3–) 4(–5), horizontal to ascending at 30°, flat, (1–)3–10(–22) cm × 1–2.5(–3) mm. Spikelets 50–150, lanceolate to ovate-lanceolate, (1.9–)2.4–2.8(–3.8) × 0.6–0.9 mm; floral scales pale brownish to transparent, midvein not winged, laterally 2–3(–4)-veined, ovate, (1.8–)2.2–3.1(–3.4) × 1–1.7 mm; stamens 2; anthers elliptic, (0.2–)0.3–0.4 mm; style 0.5–0.8 mm; stigmas 0.5–0.9 mm. Achenes light brown, stipitate, oblong, 1–1.2(–1.4) × 0.5–0.6(–0.7) mm, base cuneate to rounded, stipe to 0.1 mm, apex subtruncate, apiculate, finely papillose.

Fruiting summer. Damp grasslands, shorelines, ditches, lawns, gardens; 0–200 m; Ala., Ark., Del., Fla., Ga., Ill., Ind., Kans., Ky., La., Md., Miss., Mo., N.J., N.Y., N.C, Ohio, Okla., Pa., S.C., Tenn., Tex., Va., W.Va.; Mexico; West Indies; Central America; South America; Africa.