Flora of the Hawaiian Islands
Monocotyledon Literature for Cyperus rotundus
Wagner et al., 1990, 1999; Lorence & Wagner, 2019.
   Cyperaceae -- The Sedge Family Bibliography
      Cyperus rotundus

Common name(s): umbrella segde, kili`o`opu, mau`u mokae, nut grass
General Information
DistributionA cosmopolitan weed.In the Hawaiian Islands, naturalized on Kure, Midway, French Frigate Shoals, Ni`ihau, Kaua`i, O`ahu, Moloka`i, Lana`i, Maui, Hawai`i.

Perennial herb, rhizomes slender, elongate, deeply rooted, each one terminated by a globose or ovoid-ellipsoid tuber; culms solitary or few together, bearing a cormlike enlargement at base, slender, trigonous, smooth, erect, 10‒30(‒60) cm tall, leafy at base.
Leaves few, much shorter than the culm, folded; blade linear, 2‒5 mm wide; sheath pale brown, eventually disintegrating into brown parallel fibers; ligule short.
Inflorescences simple to compound, open, with 2‒10 slender rays of unequal length, 1‒8(‒12) cm long, spreading, spikes turbinate with short rachis, loosely bearing 3‒10 spikelets, rachis scarious-winged; involucral bracts usually 2‒3(‒5), the lowest one 2‒3 times as long as the corymb. Spikelets 8‒28-flowered, reddish brown, spreading, linear, 1‒3 cm long, 2‒3 mm wide, rachilla winged; glumes reddish brown or dark purple-red, with hyaline margin in basal portion, membranous, ovate to ovate-elliptic, 3‒3.2 mm long, folded, 5‒7-veined, keel subacute, apex obtuse or mucronate, mucro recurved; stamens 3, anthers 1–2.5 mm; style long, stigmas 3, longer than style.
Achenes brown, oblong, trigonous, ⅓‒2/5 as long as the glume, minutely puncticulate.
2n = 16, 26, 84, 96, 100, 108, 128, 152.
David Lorence