The root system of nut grass is a series of tubers that grow spikes along their sides, allowing them to stay firmly in the ground and prevent hand removal. When nut grass is not controlled, it spreads rapidly and grows faster and taller than turf grass. Nut grass also has a different green color than most turf grasses, so an infested lawn can have an unkempt appearance just days after mowing. Some herbicides can kill nut grass but instructions should be followed carefully, including all warnings on the label. The only other option is to dig weeds by hand or dig up all the soil in the lawn to 36 inches deep and screen for tubers. Minimal disturbance of the ground is best, so herbicides are the preferred control product.
Monosodium acid methanearsonate, also known as MSMA, is found in popular herbicides mixtures such as Bayer Advanced's All-in-One Weed Killer for Lawns, Acme Crabgrass and Nutgrass Killer, Green Light Crabgrass Killer and Monterrey Weed Hoe. More than one application may be needed to completely kill nut grass. MSMA has been "the herbicide of choice for postemergence control of nutsedge and other sedges in the lawn for many years," according to the Mississippi State University Extension Service. "However, several applications made two to three weeks apart may be necessary for complete control." If not in a premixed form, mix according to directions and apply with a garden sprayer.
Image (Ammonium salt of imazaquin) may require more than one application a few weeks apart to completely eliminate nut grass. It is considered effective, however, against most hard-to-control weeds, including nut grass. Apply Image herbicide when the nut grass is actively growing. Mix Image herbicide according to directions on the label and apply with a garden sprayer.
Glyphosate is the active ingredient in Roundup. It is a nonselective herbicide--it kills any plant it contacts. It can be sprayed or wiped on the leaves of the nut grass. After a week, the nut grass begins to turn yellow and decline. Be vigilant: It will regrow from the tuber, and another application is usually necessary for complete control. Apply glyphosate when the nut grass is actively growing so you can apply the herbicide to it directly. If not in an already mixed form with a sprayer attached, mix according to directions on the label and apply with a garden sprayer.
Sedgehammer (halosulfuron), formerly known as Manage, is widely available for nut grass control. It is safe to use on most warm and cool season turf grasses, but when using Sedgehammer or any herbicide, test an area of the lawn before applying it over a broad area. Apply Sedgehammer with a garden sprayer when the nut grass is actively growing.
Nutgrass 'Nihilator is the brand name of a product that contains sodium salt of bentazon as the active ingredient. It is considered a post-emergence herbicide, meaning it can be applied after the nut grass and lawn are actively growing. According to the label, Nutgrass 'Nihilator "can be used on established bluegrass, fescue, bentgrass, bermuda grass, bahia grass, centipede grass, zoysia grass, rye grass, and St. Augustine grass." Nutgrass 'Nihilator is applied when the nut grass is actively growing. Mix it according to directions on the label and apply with a garden sprayer.