2n = 112–114

Robust perennial, up to 200 cm tall, with leaves crowded at the base of culms. Leaves 1.4–3.2 × 100–200 cm, uniformly grey-green, keeled; sheath light pink to light purple-pink, soft, flexible; margin and abaxial midrib scabrid. Culm 0.8–0.9 × 60–180 cm, triquetrous, uniformly green, rarely pale brown in distal part, glabrous; upright at flowering, collapsing at seed fall. Inflorescence a terminal umbel of 6–12 unequal rays, each subtended by an involucral bract; involucral bracts 0.3–3.2 × 10–115 cm, uniformly grey-green, keeled, base green and often flushed light pink to light purple-pink or rarely pale brown. Rays 5.0–35.0 × 2.5–8.5 mm, often branched, short, stout; sheath 10–18 mm long, green, rarely brown, usually drying yellow-brown to light brown, veins sometimes red-brown; spike 40– 60 mm long. Spikelets 9.0–12.0 mm long; glumes(1.9–)2.4–3.4 mm apart on the same side of the spikelet axis. Glumes 3.0–5.8 × 2.1–2.8 mm, ovate-oblong or ovate, predominantly green, sometimes pale green or translucent, distal part and margin red-brown, usually drying yellow-brown to light brown, keeled, apex mucronate or obtuse. Ovary 0.9–1.0 × c. 0.3 mm, green to yellow-brown, triquetrous, glabrous; style 2.8–3.3 mm long, translucent, glabrous; style branches 3.3–5.5 mm long, translucent, glabrous. Anthers 1.5–2.9 × c. 0.3 mm, yellow, glabrous, apiculus 0.2–0.3 mm long, translucent, glabrous; filaments 4.8–5.2 mm long. Nut 1.6–1.7 × 0.8–0.9 mm, red-brown to orange-brown, oblong to broadly oblong, triquetrous, apex rounded, base translucent. FL Jul–Dec; FT Jul–Apr.

Cyperus insularis, sp. nov. a C. ustulato foliis bracteisque involucralibus griseo-viridibus, foliis laminis pallide roseis vel purpureo-roseis, culmo uniformiter viridi, radiis ramosis, glumis radiis bracteisque viridibus et spicibus, antheris filisque longioribus differt.