Cyperus rotundus L.

Rhizome wiry, far-extending, with prominent, ellipsoid, often fibrous-coated tubers. Stems 10–35 cm high, 3-angled, with many leaves at ± bulbous base. Leaves usually < stems, 2–3 mm wide double-folded, recurved at maturity, margins scabrid towards tip; sheaths dark brown. Involucral bracts 2–4, leaf like, lowest ± = inflorescence. Inflorescence usually a simple umbel with few slender rigid rays. Spikelets dark brown in digitate clusters of 3–10, linear, compressed, subacute, ± 5–15 × 1–2 mm. Rhachilla winged. Glumes ± 3 mm long, ± densely imbricate, ovate, obtuse, membranous, deep red-brown or red-purple with green keel, ± nerved. Stamens 3. Style-branches 3. Nut trigonous, obovoid, much < glume, rarely maturing.

[From: Healy and Edgar (1980) Flora of New Zealand. Volume 3.]