18. Cyperus iria Linnaeus, Sp. Pl. 1: 45. 1753; Boiss., Fl. Or. 5: 370. 1882; C. B. Clarke, l.c. 606; R. R. Stewart, l.c. 90; Kukkonen in Rech.f., l.c. 109.
Chlorocyperus iria (L.) Rikli, Jahrb. Wiss. Bot. 27: 564. 1895; Holm & al., World's worst weeds: fig. 95. 1977; K.M. Matthew, Fl. Tamilnadu Carnatic 4: pl.640. 1988.
Annual, 20-70 cm, solitary or forming small tussocks. Rhizome small. Stem 2-3 mm diam., trigonous, smooth. Leaves up to equalling stem; sheaths to 20 cm, soft, yellow brown, sometimes with reddish tint, finely brown-dotted, mouth margin straight; ligule 0; blades to more than 30 cm, 2-5 mm wide, flat, keeled, green or greyish green, margins slightly revolute, margins and keel towards the apex scabrous, apex acute, scabrous. Inflorescence a compound anthelodium, 5-20 cm; 4-6 bracts foliose, to more than 25 cm, much longer than inflorescence; primary branches up to 15 cm, rigid; secondary anthelodium 20-50 mm; tertiary anthelodium 20-30 mm; cluster of spikes 10-40 mm, spikate, erect, lax, with c. 40 spikes; spikes 3.5-5 x c. 2 mm, compressed, lax, with 5-20 flowers, glume-like bract c. 1 mm, glume-like prophyll scarious, bi-nerved; rachis c. 0.4 mm wide, 4-angled, flat, brown, narrowly winged, internodes c. 0.6 mm; glumes c. 1.5 mm, cymbiform, keeled, mucronate, sides nerveless, yellow-brown, shiny, margins scarious. Stamens 2; stigmas 3. Nut c. 1.2 x 0.6 mm, rather sharply trigonous, ellipsoid, brown or dark brown, finely papillose.
Fl. Per.: May - October.
Type: "Habitat in India, Osbeck.".
In fields, especially rice fields, borders of irrigation ditches; common according to R.R.Stewart (l.c. 1972); Distribution: Weed in Old World tropics and subtropics; most common in SE Asia from India to Japan and Malaysia, west to Tadjikistan, Kazakhstan and Uzbekistan (Aral Sea region), Caucasus, Iraq; E., S. and W. Africa, Madagascar; Australia and Pacific Islands; the Americas.