The label is the law. Rates and restrictions below are taken from the product labels listed under Sources. Your product's own label governs; read it before you mix or apply. Mixing calculator · Disclaimer
- Active ingredient
- Halosulfuron-methyl
- Chemical class
- Sulfonylurea; WSSA Group 2 ALS (acetolactate synthase) inhibitor.[2][1]
- Mode of action
- WSSA Group 2: ALS inhibitors (sulfonylureas)[2][1]
- Signal word
- SedgeHammer Turf Herbicide: Caution[1]
Seeding, sodding and planting after treatment
Treated lawns can be overseeded with annual or perennial ryegrass or bermudagrass 2 weeks after application. For other seeding, sodding or transplanting woody ornamentals, allow 4 weeks.[1]
Color plants and herbaceous ornamentals may be injured when planted into treated landscape areas, and newly transplanted woody ornamentals need 3 months before they can be treated.[1]
Grasses that tolerate it
Listed tolerant turf includes Kentucky bluegrass, tall and fine fescue, perennial ryegrass, creeping bentgrass, bermudagrass, St. Augustinegrass, centipedegrass, zoysiagrass, bahiagrass, kikuyugrass and seashore paspalum. It is not for golf course putting greens.[1]
Where it is used
Spray once nutsedge has reached the 3- to 8-leaf stage. A second treatment can follow 4 to 6 weeks after the first, with no more than 4 applications a year.[1]
Always add a nonionic surfactant: 2 teaspoons per gallon for small areas. If none is on hand, the label allows 2 teaspoons of common liquid dish detergent instead.[1]
For best results, don't mow for 2 days before or 2 days after treatment, and avoid spraying when rain is forecast within 4 hours.[1]
Use a level scoop, not a rounded one, and skip treatment while the turf or nutsedge is stressed, which can mean turf injury and poor control.[1]
Products and registrations
| Product | Registrant | EPA Reg. No. | Active % | Formulation | Signal word |
|---|---|---|---|---|---|
| SedgeHammer Turf Herbicide[1] | Canyon Group LLC (c/o Gowan Company, LLC) | 81880-1 | 75.0% | water-dispersible granule | Caution |
Label rates
| Product | Use | Pests | Rate |
|---|---|---|---|
| SedgeHammer Turf Herbicide | Small areas of established lawns and turf, or around established woody ornamentals (under 1,000 sq ft) | Yellow and purple nutsedge, green and annual kyllinga, plus listed broadleaf weeds | 0.9 g product per 1,000 sq ft (mixed in 1 gallon of water)[1] That is one level 0.9 gram scoop (0.03 oz) per gallon of water, plus 2 teaspoons of nonionic surfactant. Spray it within 24 hours of mixing. |
| SedgeHammer Turf Herbicide | Larger turf, golf course, landscape, fallow and non-crop areas (over 1,000 sq ft) | Yellow and purple nutsedge, kyllinga and listed broadleaf weeds | 0.67–1.33 oz product per acre[1] That's 2/3 to 1 1/3 oz per acre in 20 to 50 gallons of water with 0.25 to 0.5% nonionic surfactant. Use the low rate for light infestations and the high rate for heavy ones. |
Safety and environmental hazards
People
Signal word CAUTION: causes moderate eye irritation and is harmful if swallowed. Applicators wear long sleeves, long pants, shoes and socks, and wash hands before eating or using the toilet.[1]
Pets
The hazard statement for people and domestic animals covers eye irritation and swallowing. For lawn and landscape use, the label's re-entry rule is to keep people off treated areas until the spray has dried.[1]
Bees and pollinators
There is no bee toxicity warning, but the label says the product is toxic to plants and may harm forage and habitat for pollinators near the treated area if spray drifts.[1]
Fish and water
Toxic to non-target vascular plants; don't apply to water or where surface water is present. It can leach to groundwater and run off for months, so avoid spraying when rain or irrigation is expected within 48 hours.[1]
Common questions
- Does halosulfuron kill both yellow and purple nutsedge?
- Yes. The SedgeHammer label lists both yellow and purple nutsedge as controlled, along with green and annual kyllinga.[1]
- Can I spray SedgeHammer in flower beds?
- Only around established woody ornamentals, kept off their leaves. Don't spray it over desirable flowers, vegetables, shrubs or trees, or into food or vegetable beds.[1]
- How many times a year can I use it?
- Up to 4 applications, at least 4 weeks apart, with no more than 5 1/3 oz of product per acre in any 12-month period.[1]
Sources
- U.S. EPA Pesticide Product Label System, “SedgeHammer Turf Herbicide label, EPA Reg. No. 81880-1 (EPA-stamped, Sept. 1, 2026).” www3.epa.gov/pesticides/chem_search/ppls/081880-00001-20260901.pdf (accessed 2026-10-06)
- Weed Science Society of America, “Summary of Herbicide Mechanism of Action According to the Weed Science Society of America.” wssa.net/wp-content/uploads/WSSA-Mechanism-of-Action.pdf (accessed 2026-10-06)