Nut grass, or nutsedge, grows as a grass-like perennial weed that invades sunny areas of your landscape. Nut grass spreads quickly, reproducing by its tubers, bulbs and seeds. To control nut grass, purchase a selective herbicide labeled specifically for controlling nutsedge, with an active ingredient of halosulfuron, sulfosulfuron, trifloxysulfuron sodium or monosodium methyl arsenate (MSMA). Read the herbicide label to determine whether the specific chemical is safe for your type of grass. For example, you can't use MSMA if you have St. Augustine grass, seashore paspalum or centipede grass. MSMA is safe for use on only common or hybrid Bermuda grasses and zoysia grass.
Apply the selective herbicide to the entire lawn area where the nut grass is growing, following the exact dosage and application instructions on the label. If the nutsedge is growing in your garden, apply the selective herbicide to the individual nutsedge plants or pull out the weeds by hand.
Water the lawn area thoroughly the day after you apply the herbicide. Watering should not impede the herbicide's effectiveness, but it will protect your lawn grass from becoming injured by the herbicide.
Reapply the selective herbicide two to three months after the initial application, when you see new nutsedge shoots emerge. Don't wait more than three months to reapply the herbicide, because you won't reach all the tubers at that point.
Continue to reapply the selective herbicide to the affected lawn area every two to three months for the next two years. This will ensure that any tuber reserves beneath the ground are killed.