Purple nutsedge (Cyperus rotundus)
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Purple nutsedge is a perennial weed in the sedge family and superficially resembles grass. Nutsedges are among the most noxious weeds of agriculture in temperate to tropical zones worldwide. They are difficult to control, often form dense colonies, and can greatly reduce crop yields. In California, nutsedges are particularly problematic in summer-irrigated annual and perennial crops. Purple nutsedge is not as widespread in California as yellow nutsedge, Cyperus esculentus, and grows in the Central Valley, South Coast, and low desert to an altitude of about 820 feet (250 m). It also resembles another sedge, green kyllinga, Kyllinga brevifolia. Purple nutsedge tubers are bitter and are used medicinally in India and China.
Seedlings are rare. When found, seedling leaves are similar to that of the mature plants, but smaller. The stem base is slightly triangular and the midvein area is usually pale. The first two to three leaves emerge together, folded lengthwise.
Purple nutsedge propagates by tubers formed on underground, horizontal creeping stems called rhizomes, mostly in the upper foot of soil. Sprouts from tubers are similar in appearance to the mature plant.
The purple nutsedge stem is erect, glossy, and hairless. Although its leaves superficially resemble grass leaves, they lack collars, ligules, and auricles. The leaves of purple nutsedge are thicker and stiffer than most grasses, are V-shaped in cross-section, and arranged in sets of three from the base rather than sets of two as in grass leaves. Purple nutsedge flowering stems are triangular in cross-section; grass stems are hollow and round. Purple nutsedge can be distinguished from yellow nutsedge because it has shorter stems and grows only up to 1-1/3 feet (0.4 m) tall, whereas yellow nutsedge stems can grow to 3 feet (0.9 m) tall. Purple nutsedge leaves are dark green, 1/8 to 4/17 of an inch (3–6 mm) wide, and have rounded tips; yellow nutsedge has light green leaves, a pointed tip, and a leaf width of 1/6 to 2/5 of an inch (4–9 mm). Purple and yellow nutsedge are also distinguished by their tubers. Tubers of purple nutsedge are produced in chains, with several on a single, horizontal, underground creeping stem (rhizome), while those of yellow nutsedge are produced singly. Another similar sedge, green kyllinga, Kyllinga brevifolia, has rhizomes but no underground tubers.
Purple nutsedge spikelets are dark reddish to purplish brown with few flowers in each cluster. Yellow nustsedge spikelets are straw-colored to gold-brown with many flowers. Green kyllinga has green flowers on a compressed flower head.
Purple nutsedge does not typically produce seeds in the United States. This is in contrast to yellow nutsedge, which produces tiny single-seeded fruit.
Purple nutsedge grows mainly from tubers formed on horizontal, underground, creeping stems called rhizomes, mostly in the upper foot of soil.
Related or similar plants
- Yellow nutsedge, Cyperus esculentus
- Green kyllinga, Kyllinga brevifolia
- Smallflower umbrella sedge, Cyperus difformis
- Sedge ID illustration
- Calflora's distribution map
- For agriculture: UC IPM Pest Management Guidelines
- For gardens and landscapes: UC IPM Nutsedge Pest Note