Rice flatsedge

The height of C. iria plants varies from 8 to 60 cm. The roots are numerous, short and yellowish-red. The culms are tufted, triangular, glabrous, green and 0.6-3.0 mm thick. The leaves are linear-lanceolate, usually all shorter than the culm, 1-8 mm wide, flat, and scabrid on the margin and major ribs; leaf sheaths are green to reddish-brown, membraneous and envelope the culm at the base.

The inflorescence is simple or compound, usually open, 1-20 cm long and 1-20 cm wide, with groups of spikes which are either sessile or on 0.5-15.0 cm long peduncles (rays). Inflorescence bracts (involucre) are leafy, three to five (occasionally seven), the lower one longer than the inflorescence, 5-30 cm long, 1-6 mm wide. The spikes are sessile or almost so, elongate, and rather dense. Spikelets are erect-spreading, crowded, 6-24-flowered, 2-13 mm long, 1.5-2.0 mm wide, golden to yellowish-green.