Virginia Tech Weed Identification Guide

Rice Flatsedge: Cyperus iria

Weed Description:  An erect annual sedge that is often mistakenly identified as a grass or as one of the perennial nutsedges.  Rice flatsedge is a weed of container ornamentals, nurseries, landscapes, and turf.   Rice flatsedge is found from Florida eastward to Texas and northward to southeastern Missouri and southern Virginia.

Seedling:   Shiny, without hairs, and distinctly ridged and tougher than most grass seedlings.  No ligules or auricles occur, as would be the case with most grass seedlings.

Leaves:  Dark green, shiny, linear in outline but tapering to a point, and three-ranked.  Individual leaves may be from 3 to 8 mm wide and have rough margins toward the leaf tips.  A membranous sheath occurs at the leaf bases.

Stems: Triangular in cross-section, occurring in bunches, approximately 8 to 24 inches tall.

Roots:  A fibrous root system.

Fruit: A three-angled brown achene.

Flowers:  Terminal seedheads occur at the ends of the triangular stems.   Seedheads may reach 8 inches in length, are open, and are composed of several dense spikes.  Individual spikes are, in turn, made up of many goldish-brown spikelets that are approximately 5 to 13 mm long and 1 to 2 mm wide.  Seedheads also have 3 to 7 unequal bracts surrounding the inflorescence, the shortest one being much longer than the overall inflorescence.

Identifying Characteristics:  The shiny green ridged leaves and lack of ligule and auricles helps to distinguish this sedge from any grass weed but rice flatsedge seedlings can be easily mistaken for either Yellow Nutsedge (Cyperus esculentus), Purple Nutsedge (Cyperus rotundus), or Green Kyllinga (Kyllinga brevifolia).  However, the lack of tubers or rhizomes in rice flatsedge helps to distinguish this sedge from either yellow or purple nutsedge or green kyllinga.