Cyperus sanguinolentus

Tufted annual or perennial. Culms trigonous, smooth, 5–80 cm high, to 2 mm diam. Leaves not septate-nodulose, equalling or shorter than culms, 1–3 mm wide. Inflorescence simple with 3–5 branches to 5 cm long, or head-like; clusters subdigitate or spicate, hemispherical, to 2.5 cm diam.; involucral bracts leaf-like, 1–3 exceeding inflorescence. Spikelets flattened, 2–25 per cluster, 5–20 mm long, 2–3 mm wide in side view, 6–36-flowered; rachilla not winged, persistent; glumes obtuse, with keel 1–3-nerved, dark red-brown to blackish, margins pale, often with a hyaline patch on sides, 1.5–2.5 mm long, 1.5–2 mm wide in side view; stamens 2 or 3. Nut biconvex, broad-obovate to orbicular, brown to blackish, from one-third to one-half as long as glume, 0.8–1.5 mm long, 0.6–1.2 mm wide. Flowers spring–summer.