Nut grass (also known as nut sedge) is a real nuisance to the gardener. It robs desirable plants of water and nutrition and is unsightly in the garden or lawn. Another bad characteristic is it spreads rapidly from seeds, rhizomes and tubers.
Nut sedge lives up to its title, "One of the 10 most hated weeds." Why is it so despised? Perhaps it can be best explained by Dr. Jerry Parsons when he said, "One tuber can make 99 tubers in 90 days under good conditions." A gardener, trying to get rid of that many weeds, has good reason to hate nut sedge.
Nut grass is actually sedge
Though it resembles grass, the plant is actually sedge and is native to various areas of the world.
There are two types of nut sedge - yellow and purple.
Yellow nut sedge (Cyperus esculentus) has tubers that are smooth while purple nut sedge (Cyperus rotundus) has fibers on the outside of the tuber. If you are brave enough to taste the tubers, yellow has an almond taste, while purple has a bitter taste. The flower head of the yellow nut sedge is straw to light brown in color, and the purple is dark brown to purple.
The processes for treating them are pretty much the same, except purple nut sedge is harder to eliminate.
Control difficult, but possible
Although it is difficult to control nut sedge, it is not impossible. Selecting a weed-free site or removing weeds before actually making a garden will save a lot of time and effort. Even when making raised beds, the soil under the beds should be thoroughly treated to eliminate the weeds.
If landscaping fabric is used, one of those made from polypropylene polymer should be chosen as it will effectively suppress nut sedge growth. If nut sedge does get established in the garden, there are methods recommended to eliminate it.
- No pre-emergents control plant
Before discussing ways to eliminate nut sedge, it should be noted that there are no pre-emergents to control purple nut sedge. Those that partly reduce the number of yellow nut sedge plants and tubers include dichlobenil, and metolachlor.
- Post emergent herbicide effective
Since pre-emergents cannot eliminate the plant, a post emergent herbicide such as glyphosate, would be more effective. Spraying young plants with glyphosate will usually kill both types of nut sedges. However, it will not kill tubers under larger, more established plants. So attacking the plants while young will yield the best results, but do take care in spraying because glyphosate will kill whatever it is sprayed on.
Spraying should be done from spring to early fall. If any plants come up after spraying, those plants may be best removed by digging the tubers out to a depth of at least 16 inches.
Another suggestion to kill nut sedge is to cover the plants with a thick layer of newspaper, then cover the newspaper with a layer of mulch to improve the appearance and keep the newspaper in place. An "X" can be cut into the newspaper to plant seeds or set out plants.
The recommendation to cultivate the garden frequently for 12 weeks exposes the tubers to hot sun where they will dry up and die. This method could work if the garden is left idle for the spring and if the gardener has time to till the garden often.
- White vinegar/hydrogen peroxide treatment
Two additional procedures may have merit if the amount of nut sedge is rather small. My research suggested to allow the soil to dry out, then dig down to the root system of the nut sedge and saturate the ground with white vinegar. The second procedure suggests pouring hydrogen peroxide on the plants.
Nut sedge in turf grass can be treated with a product such as Image, Manage or MSMA. Usually, at least two treatments are required to eliminate this plant. Read all labels carefully and apply accordingly. Note that reference made to products is for educational purposes only and no endorsement is implied by Texas A&M AgriLife Extension Service.
Prevention is best remedy
While there are different suggested methods for eliminating nut sedge from the garden or lawn, the best method is prevention. All soil or other additives such as mulch or compost should be carefully checked to make sure there aren't any nut sedge tubers hiding, just waiting to make their debut.
The old adage, "An ounce of prevention is worth a pound of cure," is definitely true when dealing with nut sedge. Remember to have grass blowing away from a garden when mowing the lawn so that seeds are not thrown into it. Be vigilant at the first site of one nut sedge plant in the garden - pull or treat it to prevent it from spreading.
The Gardeners' Dirt is written by members of the Victoria County Master Gardener Association, an educational outreach of Texas AgriLife Extension - Victoria County. Mail your questions in care of the Advocate, P.O. Box 1518, Victoria, TX 77901; or vcmga@vicad.com.
Victoria County Master Gardener Association
