Cyperus flavidus

Tufted annual or perennial. Culms trigonous, smooth, 5–60 cm high, 1–1.5 mm diam. Leaves not septate-nodulose, shorter or longer than culms, mostly 1–2 mm wide. Inflorescence simple or subcompound with 2–6 primary branches to 5 cm long, or head-like; spikes ovoid to broad-ovoid, to 3 cm diam.; involucral bracts leaf-like, 2–4 exceeding inflorescence. Spikelets flattened, 5–20 per spike, 10–25 mm long, 1.5–2.5 mm wide in side view, 12–50-flowered; rachilla not winged, persistent; glumes obtuse, with 3-nerved keel, yellow-brown to very dark brown with hyaline margins, 1.5–2.5 mm long, 1–1.5 mm wide; stamens 2. Nut biconvex, obovate to elliptic, dark brown to black, less than one-half as long as glume, 0.8–1.2 mm long, 0.4–0.6 mm wide. Flowers spring–summer.