Virginia Tech Weed Identification Guide

Purple Nutsedge: Cyperus rotundus

Weed Description:  A perennial from rhizomes and tubers that may reach 2 1/2 feet in height.  The stems are 3-sided and triangular in cross section and the leaves are yellow to green in color with a distinct ridge.  Found throughout the southeastern United States as a common weed of agronomic and horticultural crops, nurseries, turfgrass, and landscapes.

Seedling:  Seedlings rarely occur.  Most plants from rhizomes and/or tubers.  Leaves do not have ligules or auricles and have a distinct ridge along the midvein, but are nevertheless often mistaken for grasses.

Stems:  Erect, unbranched, and 3-sided and triangular in cross section.  Stems are usually solitary and produce terminal spikelets.

Leaves:  Dark green in color and have a distinctly shiny appearance.  Leaves are 5 to 8 mm wide and have a distinct ridge along the midvein.  Leaves are produced in groups of 3 from the base of the plant.  Leaves are without hairs (glaucus) and no auricles or ligules are present.  The leaves of purple nutsedge taper abruptly to a sharp point, unlike the gradual taper of yellow nutsedge leaves. 
Roots: Rhizomes and tubers occur on the same plants.  Tubers are oblong, ridged, initially white in color, eventually turning brown or black, and are bitter to the taste.  Purple nutsedge produces chains of tubers that develop along the entire rhizome.
Flowers:  Spikelets occur at the ends of the solitary stems in a cluster where the flower stalks arise from a common point (umbel-like).  Individual spikelets are reddish-purple to reddish-brown in color.
Identifying Characteristics:  Yellow Nutsedge (Cyperus esculentus) is very similar in appearance and growth habit to purple nutsedge, and the two are often confused.  However, the leaves of yellow nutsedge taper to a point gradually whereas those of purple nutsedge taper to a point abruptly.  Additionally, the seedhead of yellow nutsedge is yellow in color, while that of purple nusedge is purple.  Lastly, the tubers of purple nutsedge are often connected in chains and bitter to the taste, while those of yellow nutsedge are solitary and sweet to the taste.  Rice flatsedge (Cyperus iria) and Green Kyllinga (Kyllinga brevifolia) are also similar when young, however rice flatsedge has a fibrous root system and green kyllinga has rhizomes that are usually red to purple in color.