(fotografato a Tor Caldara - Lazio)
Cyperus polystachyos Rottb.
ZIGOLO TERMALE
Cyperaceae. Tufted annual or perennial with short rhizome.
Culms trigonous to triquetrous, smooth, 10–60 cm high, 1–2.5 mm diam.
Leaves not septate-nodulose, shorter than culms, 2–3 mm wide. Inflorescence simple or subcompound with 3–8 primary branches to 6 cm long, or head-like; clusters subdigitate, broad-obovoid to hemispherical, to 40 cm diam.; involucral bracts leaf-like, 2–4 exceeding inflorescence. Spikelets flattened, numerous per cluster, 5–25 mm long, c. 1.5 mm wide in side view, 10–50-flowered; rachilla narrowly winged, persistent. Glumes obtuse, short-mucronate, with 3-nerved midrib, 1.7–2.5 mm long, pale yellow to red-brown, with whitish margins. Stamens 2 or rarely 1. Style 2-fid.
Nut biconvex, narrow-obovate, about half as long as glume, 1–1.2 mm long, 0.4–0.5 mm wide, red-brown to blackish.
Fiorisce maggio - ottobre. Pianta rara a protetta.