Nutgrass infestations of lawns and gardens are difficult to eradicate or control. This annoying condition is caused by the plant’s extensive tubular (nutlet) root system that goes deep and wide underground. These rhizome or chain-strand roots are the main source of nutgrass renewal, more so than from the seeds of their flowers. Because nutgrass keeps a continuous reservoir of dormant roots (nutlets), it has an endless supply future growths. Thus, when one growth of shoots is treated or removed, another growth or two will sprout up nearby. To minimize nutgrass growth, its root system must be destroyed, which is not a simple one-time-treatment task.
What is nutgrass or nutsedge?
Nutgrass is a heavy perennial grass of the sedge family. Technically, two common varieties of it (purple and yellow nutgrass) are called cyperus rotundus and cyperus esculentus, respectively. Nutgrass is also called water grass because it likes moisture, tight soil, and lots of hot sunshine. It’s often recognized as the fast-growing taller grass that appears shortly after mowing a lawn. Its course grass-like shoots (three-to-five or more per plant) are each slightly triangular or V-shaped with a strong vertical vein going down the middle of each. Often, the yellow variety is a lighter green than the surrounding lawn. Nutgrass is invasive. It will spread without some kind of controlling treatment. It goes dormant in the autumn of winter climates, but will reappear the following late spring.
Five common treatments for controlling nutgrass are available to the homeowner and consumer. Each one, listed below, can be done in a safe manner. But none of them are effective one-time cures. Overall, the two herbicide treatments listed below (4 and 5) appear to be effective means for controlling it at this time. However, the chemical treatments must done safely by following the product’s written directions for use. Herbicide appliers could also read and know the products material-safety-data-sheets (MSDS).
1. Mechanically disturbing it. Plowing, cultivating, tilling, or digging-up the ground, and then sifting out the nutgrass roots. This treatment works. But it has to be repeated often, which eliminates it as a lawn treatment, and makes it impractical for treating crowded gardens.
2. Pulling or weeding it. This treatment will make the shoots disappear for a while. However, most of its original roots are still submerged underground. Thus, these plants will soon return, often more of them than before.
3. Smothering it. Covering the infected area with sheeting, e.g., cardboard, plastic, plywood, canvas, or mulch. This treatment will slow nutgrass down for a while, but won’t stop or kill it. Nutgrass will pierce its way through cardboard, cloth, plastic, and mulch. Also, its covered roots will remain dormant for return growths once the covering is removed or wears thin. Additionally, the nutgrass will spread to the outside of the covering, underground.
4. Spraying it with a diluted herbicide solution. Spraying the infected area with a chemical formula purchased at local gardening outlets is a common choice among busy homeowners. This treatment works okay with repeated applications, done at consumer’s risk. The applications generally are done when no rain or dampness is in the forecast. Also, commercial lawn-care companies can do this treatment effectively; actually, they are a good choice for a safe, more expensive cure.
Still, the main herbicide chosen for the treatment must be compatible with the infested yard in question. For example, one herbicide will work well with some grasses, but will harm others. Also, a lawn-compatible herbicide could harm the lawn if applied too often or too strongly. Additionally, another herbicide can be used on the lawn, but it cannot be used near vegetable or ornamental plants. Thus, the applier of the spray must be careful both in choosing the herbicide and applying it.
Also, the more recent urea-type herbicides, like, halosulfuron-methyl, appear to work well on the nutgrass infested lawns if applied regularly and seasonally for two or more years. It can take that long to minimize the nutgrass root system, depending on how well its start is. This kind of spraying can reduce infestations over large areas of ground.
5. Spot-treating it with a strong herbicide solution. Applying a strong herbicide solution to the individual nutgrass plants can be done with a narrow-stream spray-bottle or a thick artist’s paint brush. This treatment is best suited for mild infestations of nutgrass or fairly small patches of it. (Note: if an entire lawn is heavily infested, it might be best to 1) kill the whole yard with a total vegetation killer, 2) plow or till up its ground while sieving out the nutlets, and 3) reseed it after a short waiting period. Vegetation killers do not destroy the ground itself, rather, only the vegetation growing on it. If in doubt about this step, obtain a professional opinion first.)
Yet, during the spot-treatment of nutgrass, the herbicide solution must be applied to the nutgrass leaves directly, again at the consumer’s risk. The herbicide will then translocate from leaves to the stem and roots. Also, applying a daub of the solution onto the plant’s leaf-crotch at the stem helps to kill the plant, but the bulk of the application must go onto the leaves for a good uptake that will reach the roots. Additionally, the applier must keep the solution from touching the surrounding grasses or plants as much as possible, especially if the chemical is a kill-all herbicide.
Glyphosate (organic-salt), a well-known main ingredient of kill-all-vegetation herbicides, can be used here. A 12-to-16-oz bottle of 41% liquid concentrate can be purchased for about $10 at local outlets. Glyphosate is fairly nontoxic to humans, but it must still be handled safely by wearing rubber gloves and other apparel. This concentrate can be applied to the nutgrass shoots by first diluting it with water anywhere from a 1:1 to 1:20 concentration in a small capped container. First-time users might want to start with a 1:20 solution to test how the process works by trial and error, while working up to a stronger concentration. Also, home owners having delicate grasses and ornamental plants will want to use a dilute glyphosate solution to start with, like, 1:20 or more, which is much closer to the diluted spray concentrations. Furthermore, the halosulfuron-methyl herbicide mentioned above in #4 can be used for spot-treating nutgrass by following the product’s directions for diluting it to a powerful spray concentration (0.9-g granules/gallon) for about $15.
Certain sources suggest adding other ingredients to these kind of solutions, like, the adding of a surfactant (dish soap), hydrogen peroxide, vinegar, or a particular salt to make it stick to the leaves better, or to help it absorb through them faster. But, none of these additions are necessary. Also, such mixtures can yield slight chemical alterations over time, which will give undesirable results by not working well at all, or by the killing of adjacent grasses and plants inexplicably. Yet, when freshly-made spot-treatments are done carefully, the nutgrass will die in about one-to-two weeks without causing excessive disturbances to the surrounding vegetation.
Six-day appearances of yellow nutgrass after spot-treatment with 20% glyphosate solution.
- Shoots slightly limp; no color change
- Shoots more limp; slight color change to amber
- Shoots touch the ground; overall color is more amber
- Shoots start to wither; color is still more amber
- Shoots lay on ground and begin to curl; only slight yellow-green color left
- Shoots are withered straw-like stalks lying on the ground or lawn
Spot-treating nutgrass with a strong herbicide solution is time-consuming, and requires substantial patience to carry out, especially when the home/yard owner does it alone. Undoubtedly, his/her neighbors will ask, “Hey! What are you doing there?” But, this fairly inexpensive treatment works well for minimizing nutgrass infestations if the solution is handled and applied carefully at the owners discretion. Once the main infestation is under control, it’s fairly easy to suppress any new growths with continued spot-applications.
At this time, the spraying or spot-treating of common nutgrasses with carefully selected herbicide solutions appears to be an effective means for minimizing its infestations of yards and gardens. These treatments can be done by the yard/garden-owners themselves at their own risks, or by hired professionals.