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Publication #SP 37

Purple Nutsedge, Cyperus rotundus L.1

David W. Hall, Vernon V. Vandiver, and Jason A. Ferrell2

Classification

Common Name: Purple Nutsedge

Scientific Name: Cyperus rotundus L.

Family: Cyperaceae, Sedge Family

Seedling

Two or three leaves emerge from the ground simultaneously (Figure 1). The blades are linear, folded lengthwise, smooth, membranous, light green, and overlapping to form a somewhat triangular structure in cross section. The bud leaves are erect. The sheaths are tubular.

Figure 1. 

Seedling, Purple Nutsedge (Cyperus rotundus L.).


[Click thumbnail to enlarge.]

Mature Plant

Purple Nutsedge is a smooth, erect, perennial sedge (Figure 2). It has a fibrous root system which is extensively branched. The plant spreads by means of slender rhizomes. Its tubers are white and succulent when young, turning brown or black and fibrous with age. The erect, simple culms are smooth, solid and triangular in cross section. The culms are frequently up to 36-40 cm tall, occasionally to 70 cm, and have been found to reach 100 cm on moist fertile soils. The leaves originate from the base of the plant. They are linear with sharp tips and may be much shorter than, or as long as, the culm is tall, and are usually not more than 5 mm wide. The leaves are smooth, shiny, dark green and grooved on the upper surface. The seedhead consists of 3-8 unequal, slender, three-sided stalks. The red to purplish brown spikelets are up to 3.5 cm long and 2 mm wide and are clustered at the ends of the stalks. Each spikelet is made up of from 10-40 individual flowers. The fruit is 1.5-2 mm long, 1.5 mm wide, triangular in cross section, grayish brown and dull. Both the apex and the base of the fruit are rounded. The seedhead is subtended by 2-4 leaf-like bracts, about as long as, or shorter than, the seedhead.

Figure 2. 

Mature plant, Purple Nutsedge (Cyperus rotundus L.)


[Click thumbnail to enlarge.]

History

The genus name Cyperus is from Cypeiros which was the ancient Greek name for the genus. Rotundus is Latin for round and refers to the tuber.

Habitat

C. rotundus occurs in disturbed areas throughout Florida and the southeastern United States. It is widely distributed throughout both the tropical and warmer temperate regions of the world.

Biology

Most of the success of this troublesome weed is due to its ability to survive and reproduce from tubers during adverse conditions. It grows well in almost every soil type, over a wide range of soil moisture, pH and elevation, and can survive the highest temperatures encountered in agriculture. It does not tolerate shaded areas. Temperature and shade seem to be the most important factors in natural control of this weed. The plants also reproduce by seeds but this is negligible since seed germination seldom averages more than 1-5%. The production of an active substance in the underground parts of the plant has an inhibitory effect on the root and shoot development of cucumber, barley and tomato plants. Tuber production in Buckwheat [Fagopyrum esculentum] and Teff [Eragrostis tef (E. Abyssinica)] was also affected.

Control

Peanuts

Control of purple nutsedge with preemergence herbicides is difficult to achieve. However, purple nutsedge suppression is commonly observed with Dual Magnum, Pursuit and Strongarm. However, Dual Magnum is less effective on purple nutsedge than on yellow, while Pursuit is somewhat more effective on purple. Regardless, only if weed density is relatively light will these herbicides alone be sufficient. Paraquat plus Storm or Basagran has some purple nutsedge activity, but results will often be inconsistent and less than desirable.

Postemergence applications of Basagran can be used to control yellow nutsedge. However, Basagran is not effective against purple nutsedge. Cadre or Pursuit can be used to control purple nutsedge, but Cadre is much more effective than any other postemergence herbicide option. Cadre will consistently give greater than 90% purple nutsedge control.

Cotton

There have traditionally been few products that provide acceptable control of purple nutsedge in cotton. There are no preemergence options and MSMA or glyphosate were the only options for postemergence or postdirected applications. However, MSMA and glyphosate are not highly effective on purple nutsedge and will generally give less than 70 or 80% control. Envoke herbicide (registered in 2004) has immediately become the standard for sedge control. This is because Envoke will consistently give >90% sedge control. The most effective postdirected herbicide option is Suprend (a combination of Caparol and Envoke).

Footnotes

1.

This document is SP 37, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date May 1991. Revised April 2003. Reviewed January 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

David W. Hall, former extension botanist, Herbarium, Florida Museum of Natural History; Vernon V. Vandiver, associate professor emeritus, Agronomy Department; Jason A. Ferrell, assistant professor, Agronomy Department; Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication does not signify our approval to the exclusion of other products of suitable composition.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.