Nutsedge

Pesticides updated by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University, 10/13. Originally prepared by Karen Russ, HGIC Horticulture Information Specialist; and Chuck Burgess, HGIC Horticulture Extension Agent, Clemson University. Revised by Joey Williamson, HGIC Horticulture Extension Agent, Clemson University. New 11/04. Images added 10/09.

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Nutsedges are very aggressive and persistent weeds that commonly infest lawns, vegetable and flower gardens, and home landscapes. They can be very difficult to eradicate and their control is likely to be a long process. Successful control involves both cultural and chemical management methods.

Once a nutsedge infestation has been controlled, sanitation to prevent new introductions is critical. Any new infestations should be managed right away to prevent spread of these aggressive and difficult-to-control weeds.

Yellow nutsedge (yperus esculentus)
Yellow nutsedge (Cyperus esculentus).
Photo by Joseph LaForest, University of Georgia, Bugwood.org

Life Cycle & Description

Nutsedges are often called "nutgrass" because they closely resemble grasses. Correct identification is very important, as most herbicides for grass control are not effective on sedges. Nutsedges can be distinguished from grasses by their stems, which are triangular or V-shaped in cross section, while grass stems are hollow and round. Their leaves are thicker and stiffer than most grasses and are arranged in groups of three at the base. Nutsedge leaves appear creased with prominent mid-veins.

Most nutsedges are perennials whose leaves die back in the fall when temperatures decrease. Tubers (often called "nutlets") and rhizomes (underground stems) survive in the soil and sprout the following spring. The tubers and rhizomes can grow eight to 14 inches below the soil surface.

Nutsedges thrive in almost any kind of soil. While they prefer moist soil, established nutsedge plants will thrive even in dry soil. They spread by small tubers, by creeping rhizomes or by seed. New tubers begin forming four to six weeks after a new shoot emerges. Individual nutsedge plants may eventually form patches 10 feet or more in diameter.

Purple nutsedge (Cyperus rotundus)
Purple nutsedge (Cyperus rotundus)
Photo by Joseph LaForest, University of Georgia, Bugwood.org

Identifying Nutsedges

Purple nutsedge (Cyperus rotundus) and yellow nutsedge (Cyperus esculentus) are the most common nutsedges in South Carolina. Yellow nutsedge is more widespread than purple nutsedge due to its greater cold tolerance. However, where purple nutsedge is adapted, it can be even more vigorous than yellow nutsedge. The two species often grow together. Because purple and yellow nutsedge differ in herbicide susceptibility, correct identification is critical to successful control.

Identifying Characteristics of Nutsedges
Yellow Nutsedges Purple Nutsedges
Long Tapered leaf tip Leaves taper abruptly to a blunt point
Seed head yellow Seed head purple
Tubers single at tips of rhizomes Tubers connected in chains on rhizomes
Emerges early Emerges later
Leaves light green Leaves darker green
12 to 16 inches tall when mature Usually under 6 inches when mature

Control in the Lawn

A combination of cultural, mechanical and chemical control methods has the best chance of effectively managing nutsedge.

Cultural Control: Nutsedges thrive in moist areas and their presence often indicates that drainage is poor, irrigation is too frequent, or sprinklers are leaky. Once established, however, they will tolerate normal moisture levels or even drought.

Nutsedge tubers are spread by cultivation and introduced in topsoil and nursery stock. They can persist in the soil for years. Learn to recognize nutsedge to avoid accidentally bringing it in on newly purchased sod, topsoil, or plants. Be sure to thoroughly clean tools and equipment such as tillers that have been used in an infested area to avoid spreading tubers and rhizome pieces.

Give turfgrasses a competitive advantage by following all recommended practices for the lawn species including mowing at the ideal height, applying fertilizer at the proper rate and time, and maintaining the ideal soil pH. Proper irrigation amounts and timing are especially important, since excessively moist soil will encourage the growth of nutsedge. Monitor and manage insect and disease infestations to avoid thin, bare areas that may be overtaken by nutsedge.

Mechanical Control: It is possible to eliminate very small patches of nutsedge by digging. Dig at least 10 inches deep and at least eight to ten inches beyond the diameter of the aboveground leafy portion of the plant. This will ensure removal of the spreading tubers. This is best done early in the spring, before more tubers are produced.

Chemical Control: Nutsedges can be controlled chemically with postemergence herbicides. Because different herbicides are effective against different species, it is important to correctly identify the nutsedge to be controlled. Herbicides also vary regarding the desirable plants they can be safely used around without causing damage. Always check the label to make sure the pesticide you choose will not damage desired plants.

Herbicides for Nutsedge Control in Home Lawns
  Sedge Control Turf Tolerance
Herbicide Yellow Nutsedge Purple Nutsedge Bermuda Centipede Tall Fescue St. Augustine Zoysia
E=Excellent; G=Good; F=Fair; P=Poor
S = Safe when used according to the label.
I = Intermediate tolerance, use with caution, use at reduced label rates, or minimum label rates.  
NR = Not registered for use on this turf species.
Basagran T/O (bentazon) G P S S S S S
Image Nutsedge Killer (imazaquin) F G S S NR S S
SedgeHammer (halosulfuron) G-E G-E S S S S S
SpectracideWeed Stop for Lawns Plus Crabgrass Killer (sulfentrazone) F P-F S S S NR S

Apply herbicides when nutsedge is actively growing in warm conditions with adequate soil moisture. Applications during droughty conditions or when the nutsedge is not actively growing may result in poor control. Avoid applications during hot or dry weather to minimize the chances of injury to the turfgrass. Follow the instructions on the product label for the most effective application rate and procedure.

Avoid mowing before a postemergence herbicide application to allow for adequate foliage to absorb the herbicide. Also avoid mowing for two days after application to allow enough time for the plant to absorb and move the herbicide down to the tubers. The length of time to allow before and after mowing varies with the product. Always read the label for specific instructions.

Bentazon (the active ingredient in Basagran T/O and Lesco Lescogran) is labeled for use on fescue, bermudagrass, zoysiagrass, centipedegrass, St. Augustinegrass and other turfgrasses. It should not be applied to any newly seeded or newly sprigged turf until after it is well established. Rainfall or sprinkler irrigation within eight hours of application may reduce the effectiveness.

Imazaquin (the active ingredient in Image Nutsedge Killer) is recommended for centipedegrass, zoysiagrass, St. Augustinegrass, and bermudagrass lawns. For best weed control, the application must be followed by one half inch of irrigation to wash the active ingredient into the shoot/root zone. Repeat application may be necessary in 3 to 5 weeks for complete control. Do not apply Image Nutsedge Killer to newly seeded or newly sprigged turf and do not apply during periods of slow growth. Furthermore, due to its preemergence activity, treated areas cannot be seeded or over-seeded for six weeks.

Halosulfuron (the active ingredient in SedgeHammer, Hi-Yield Nutsedge Control and in Monterey Nutgrass Killer) is effective against both yellow and purple nutsedge. These products require the use of a nonionic surfactant (such as Southern Ag Surfactant for Herbicides) at 2 teaspoons per gallon of water, and treatment may need to be repeated in 3 to 4 weeks for complete control.

Sulfentrazone (one of the active ingredients in Spectracide Weed Stop Weed Killer for Southern Lawns Concentrate, and Spectracide Weed Stop for Lawns Plus Crabgrass Killer) is faster acting on nutsedges, but may require a second application.

Penoxsulam (the active ingredient in the granular product Green Light Wipe-Out Tough Weed Killer for Lawns) and sulfentrazone will both give good control of annual nutsedges.

Control in the Landscape

Cultural Control: Prevent nutsedge in the home landscape by avoiding its introduction, which is often from trucked-in soil. Be certain before purchasing bulk soil that it is not infested with tubers. Another source is from nursery plants that are infested with nutsedge. Reject plants that contain any visible nutsedge.

Maintain proper moisture levels in the landscape. Excessive irrigation will encourage the growth of nutsedge. If the area is poorly drained, improve drainage by installing drains or grading soil so that water flows away from planting beds.

Nutsedges do not grow well in shade. By changing landscape plantings you may be able to reduce their growth this way. For example, a highly infested, annually planted flower bed may be better off replanted with a tall, dense, ground cover or shrub that would shade out the nutsedge. Low-growing ground covers will not shade out yellow nutsedge.

Mechanical Control: Nutsedge reproduces primarily from tubers that can lie dormant and remain viable for several years. Unfortunately, these tubers do not break dormancy and begin to grow at the same time. Thus, their removal should be viewed as a long-term process.

Small patches can be dug out, making sure that all tubers are removed by digging deep and wide. Also, landscape fabrics can be used around shrubs and trees to shade out and retard the growth of nutsedge.

Chemical Control: Bentazon (such as in Basagran T/O, Hi-Yield Basagran and Lescogran) can be used as a spot treatment for yellow nutsedge near ornamental trees and shrubs. It will injure the roots of rhododendron and sycamore but can be applied over the top of some ornamental plants as listed on the label.

Products containing halosulfuron (such as SedgeHammer) can be used as a spot treatment for purple nutsedge near ornamental trees and shrubs. Unlike Basagran T/O, contact of SedgeHammer with foliage of any ornamental plant should be avoided.

Image Nutsedge Killer damages many popular landscape plants such as viburnum, pieris, azalea, birch, abelia, ligustrum and many hollies through root and foliar contact. Use Image Nutsedge Killer with caution in most landscapes.

Efficacy of Herbicides for Nutsedge Control in Landscapes
Herbicide Yellow Nutsedge Purple Nutsedge Over the top application
E=Excellent; G=Good; F=Fair; P=Poor
bentazon (Basagran T/O) G P Limited species, check label
halosulfuron (SedgeHammer & other brands) G-E G-E Spot sprays only
imazaquin (Image Nutsedge Killer) F G Limited species, check label

Control in the Vegetable Garden

Cultural Control: Nutsedges thrive in moist areas and their presence often indicates that drainage is poor, irrigation is too frequent, or sprinklers are leaky. Once established, however, they will tolerate normal moisture levels or even drought.

Nutsedge tubers are spread by cultivation, and introduced in topsoil, where they can persist for years. Learn to recognize nutsedge to avoid accidentally bringing it in on newly purchased topsoil. Be sure to thoroughly clean tools and equipment such as tillers that have been used in an infested area to avoid spreading tubers and rhizome pieces.

Since nutsedges do not grow well in shade, areas of the vegetable garden can be rotated into a solidly planted, dense, relatively tall crop such as beans or southern peas for a season. This will reduce the amount of nutsedge in the garden over several seasons.

Mechanical Control: Control of nutsedge should be viewed as a long-term process. Pulling the plants out by hand is relatively ineffective because tubers deep in the ground usually break off the pulled shoots. Very young plants can be controlled by hand weeding or hoeing if they are consistently weeded out before they have five to six leaves. In summer this will require weeding at least every two to three weeks, but doing so will cause a depletion of energy reserves and resprouting will soon stop. Once nutsedge plants have more than five or six leaves, they begin to form tubers, usually in May or June. Mature tubers can resprout as many as 10 to 12 times.

Using a tiller to destroy mature plants will only spread the infestation, as it moves the tubers around in the soil. However; repeated, frequent tilling of small areas before the plants have six leaves can gradually reduce populations. Tilling for nutsedge suppression should be limited to times when the soil is dry. Tilling when soil is wet is more likely to move tubers into new areas, as they adhere to equipment.

It is possible to eliminate very small patches of nutsedge by digging. Dig at least 10 inches deep and at least eight to 10 inches beyond the diameter of the aboveground leafy portion of the plant. This will ensure removal of the spreading tubers. Removal by digging is best done early in the spring, before more tubers are produced.

Chemical Control: Glyphosate can be used to control nutsedge in vegetable gardens. Examples of products containing glyphosate are Roundup Original, Eraser Systemic Weed & Grass Killer, Quick Kill Grass & Weed Killer, Bonide Kleenup Grass & Weed Killer, Hi-Yield Super Concentrate Killzall Weed & Grass, Maxide Super Concentrate 41% Weed & Grass Killer and Southern States Grass & Weed Killer Concentrate. Glyphosate will damage or kill crop plants if it touches their foliage. Care must be taken to avoid damaging plants with spray drift. Repeat applications as new plants emerge.

Certain formulations of bentazon (such as in BASF Basagran T&O and Arysta Basagran) are labeled for use around a very few vegetable crops – beans, corn, peas and peanuts only. Always read the pesticide label for specific instructions.

Pelargonic acid is the main active ingredient in Scythe herbicide, which is labeled for use around many vegetables. Scythe is a non-selective, contact herbicide that will damage any foliage it touches, so care must be taken to protect crop plants from contact or drift. Repeat applications as new plants emerge. Scythe is a severe eye irritant. Always read the pesticide label for specific instructions.

Pesticide Safety

Always read the pesticide label and follow its directions exactly. You may only use the pesticide on sites or crops listed on the label. Be sure to observe all special precautions that are listed on the label. Wear protective clothing or equipment as listed on the label when mixing or applying pesticides. Mix pesticides at the rate recommended for the target site as listed on the label. Never use more than the label says. Follow all label directions for safe pesticide storage and disposal. Always remember to read and heed the six most important words on the label: "KEEP OUT OF REACH OF CHILDREN.

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This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. All recommendations are for South Carolina conditions and may not apply to other areas. Use pesticides only according to the directions on the label. All recommendations for pesticide use are for South Carolina only and were legal at the time of publication, but the status of registration and use patterns are subject to change by action of state and federal regulatory agencies. Follow all directions, precautions and restrictions that are listed.