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Federal Noxious Weed
TDA Noxious Weed
TPWD Prohibited Exotic Species
Invasive Plant Atlas of the US

NOTE: means species is on that list.

Cyperus rotundus


Nutgrass

Synonym(s):
Family: Cyperaceae (Sedge Family)
Duration and Habit: Perennial Grass/Grasslike


Photographer: Charles T. Bryson
Source: USDA Agricultural Research Service, Bugwood.org

Description

Purple nutsedge is a perennial which rarely reproduces by seed but extensively reproduces by rhizomes which initially are white and fleshy with scale leaves, later becoming ligneous or "wiry." Rhizomes either extend upward, horizontally, or downward. Those which extend upward swell upon reaching the surface to form what is variously called a basal bulb, a tuberous bulb, or a corm that is 0.3 to 1 cm in diameter and produces shoots, roots, and other rhizomes. Those which extend horizontally or downward give rise to tubers that repeat the cycle to form other tubers in a chain or to form new shoots (21, 28, 38). The tubers vary in length from 0.75 to 3.5 cm and in widths from 0.3 to 1 cm. The leaves are three-ranked, shiny, dark green, and corrugated in cross section. They are 6 to 10 mm wide and 10 to 35 cm long. The rachis, which grows through the center of the leaf bundle, is erect, simple, smooth, triangular in cross section, and 10 to 60 cm long. The rachis supports a terminal inflorescence which is a simple or slightly compound, loose umbel. Each inflorescence is subtended by two or more involucral leaves or leaf-like bracts that are as long or longer than the flower-bearing rays. The rays are formed from three to nine slender, spreading, three-sided peduncles of unequal length. Near the ends are clusters of narrow spikelets, 0.8 to 2.5 cm long and 2 mm wide, 10- to 40-flowered, acute and compressed with a red, reddish-brown, or purplish-brown color. They possess glumes, 2 to 3.5 mm long, which are ovate and nearly blunt with three to seven nerves. Individual seeds are achenes, 1.5 mm long, which are ovate or oblong-ovate, three-angled, dull olive-gray to brown or black in color covered with a network of gray lines. Each achene is sessile on the spikelet and is subtended and covered by a single scale or glume, which is ovate 2 to 3.5 mm long, and nearly blunt with three to seven nerves.

Ecological Threat: Infests crop production areas in tropical and temperate climates, causing large losses in crop yields.

Biology & Spread: Herbaceous perennial weeds that are among the worst pests known. Exhibits prolific vegetative activity which produces a complex underground system of basal bulbs, rhizomes, and tubers. Shoots arise from the basal bulbs as a fascicle. Basal bulbs are a primary site for prolific vegetative growth because they contain the meristems for leaves, rhizomes, roots, and flower stalks. The tubers contain quiescent buds and function like the seeds of annuals, acting as the primary dispersal units. Tubers are produced on rhizomes and lie dormant in the soil for extended periods. They germinate under the appropriate environmental conditions to produce plants that perpetuate the infestations.

History: The sedge family represents a diverse group of plants which has been used to make paper, rain garments, and mats, has been eaten, brewed, or used as medicine, and has been grown as ornaments. About 7% of the 3,000 species of Cyperaceae interfere with crop production and, therefore, are considered to be weeds. Two species, purple and yellow nutsedge (Cyperus rotundus L. #1 CYPRO and C esculentus L. # CYPES), rank among the world's worst weeds. Both are perennials, propagate vegetatively, and resist many control practices commonly used in modern agriculture. Interference during the crop establishment phase and increased costs of control are important reasons for studying these weeds and developing management strategies that minimize their effect on crop production.

U.S. Habitat: Found in croplands, waste places, and home gardens.

Distribution

U.S. Nativity: Introduced to U.S.

Native Origin: Not Found (Bailey, L.H. and E.Z. Bailey, Hortus Third: A Concise Dictionary of Plants Cultivated in the United States and Canada, MacMillan Publishing Co., Inc., New York , (1977).); NatureServe Explorer

U.S. Present: AL, AR, AZ, CA, DE, FL, GA, HI, KY, LA, MD, MN, MO, MS, NC, NJ, NY, OK, PA, PR, SC, TN, TX, VA, VI

Distribution: In the continental United States, purple nutsedge is found in the southeast from Texas to Virginia and in California.

Mapping

Invaders of Texas Map: Cyperus rotundus
EDDMapS: Cyperus rotundus
USDA Plants Texas County Map: Cyperus rotundus

Invaders of Texas Observations

List All Observations of Cyperus rotundus reported by Citizen Scientists

Resembles/Alternatives

Management

Herbicides- Most soil-applied herbicides used for selective control of yellow nutsedge inhibit shoot and rhizome emergence but have little activity against parent tubers. Recent evidence suggests that infestations can be reduced to manageable levels in a few years if new tuber development is inhibited. In Oregon, for example, dichlobenil (2,6-dichlorobenzonitrile) has reduced infestations of yellow nutsedge (var. leptostachyus) by 90 to 95% in perennial horticultural crops and landscapes when applied under cold conditions and incorporated with rain in midwinter. Thiocarbamate herbicides inhibit sprouting of new shoots and rhizomes; but mature tubers remain viable, and resprouting occurs following sufficient herbicide degradation. In contrast, metolachlor' [2-chloro -N-Q(2-ethyl-6- methylphenyl) - N- (2 - methoxy- 1- methylethyl)acet- amide] provides consistent control of mature tubers while inhibiting new shoots and rhizomes. Tuber populations in the Pacific Northwest have been reduced by 90% with either fallow applications of metolachlor in the fall or midwinter or preemergence treatments in the spring. Activity of most postemergence herbicides is improved when nutsedge plants are growing vigorously. However, these herbicides must be applied before new tubers form since maturation into viable propagules occurs quickly. Bentazon [3 -(1 -methyl- ethyl) - (1H) -2,1,3- benzothiadiazin -4( 3H) -one 2,2 - dioxide], for example, controls yellow nutsedge when applied in split treatments 7 to 10 days apart with a nonphytotoxic oil to young plants with 4 to 6 leaves. Complete coverage of nutsedge foliage is essential, and temperatures must exceed 24 C. Other foliar-applied herbicides such as paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) and glyphosate [(N-phosphonomethyl)glycine] will control growing nutsedge plants and arrest rhizome and tuber development when applied at the 4- to 6- leaf stage before tubers begin to enlarge. Glyphosate treatments following tuber development, however, result in small, but viable, propagules which lead to significant population increases

USE PESTICIDES WISELY: ALWAYS READ THE ENTIRE PESTICIDE LABEL CAREFULLY, FOLLOW ALL MIXING AND APPLICATION INSTRUCTIONS AND WEAR ALL RECOMMENDED PERSONAL PROTECTIVE GEAR AND CLOTHING. CONTACT YOUR STATE DEPARTMENT OF AGRICULTURE FOR ANY ADDITIONAL PESTICIDE USE REQUIREMENTS, RESTRICTIONS OR RECOMMENDATIONS. MENTION OF PESTICIDE PRODUCTS ON THIS WEB SITE DOES NOT CONSTITUTE ENDORSEMENT OF ANY MATERIAL.

Text References

Bendixen L.E. and U.B. Nandihalli. 1987. Worldwide Distribution of Purple and Yellow Nutsedge (Cyperus rotundus and C. esculentus). Weed Technology 1:61-65.

G.D. Wills. 1987. Description of Purple and Yellow Nutsedge (Cyperus rotundus and C. esculentus. Weed Technology 1:2-9.

Phatak, S.C., M.B. Callaway, and C.S. Vavrina. 1987. Biological Control and Its Integration in Weed Management Systems for Purple and Yellow Nutsedge (Cyperus rotundus and C. esculentus. Weed Technology 1:84-91.

Stoller, E.W and R.D. Sweet. 1987. Biology and Life Cycle of Purple and Yellow Nutsedges (Cyperus rotundus and C. esculentus. Weed Technology 1:66-73.

William, R.D. and L.E. Bendixen. 1987. Year-Round Management of Yellow Nutsedge (Cyperus esculentus): An Extension Worker's Summary. Weed Technology 1:99-100.

Online Resources

Search Online

Google Search: Cyperus rotundus
Google Images: Cyperus rotundus
NatureServe Explorer: Cyperus rotundus
USDA Plants: Cyperus rotundus
Invasive Plant Atlas of the United States: Cyperus rotundus
Bugwood Network Images: Cyperus rotundus

Last Updated: 2008-11-24 by LBJWFC
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