Few things are more frustrating than trying to rid an otherwise beautiful lawn of nut grass. Nut grass is in the sedge family and belongs in the genus Cyperus. There reside the two worst weeds that can afflict lawns. Yellow nut grass (Cyperus esculentus) and purple nut grass (Cyperus rotundus) are the most common of all the sedges and can be tough to control. Both sedges are herbaceous perennials, reproducing from underground tubers. Once a program is established to kill the nut grass, it is important to follow through or the grass will grow back.
Identify which type of nut grass is growing in the lawn, since no one, selective herbicide will kill both species. Identifying the type of nut grass will allow you to choose the correct herbicide that will only target the particular grass and not harm other vegetation.
Distinguish the grass by the flower, as yellow nut grass flowers will be yellower than the bloom on purple nut grass. The leaf tips are pinched on yellow nut grass. Purple nut grass has keeled leaves, as in a boat.
Use the pre-emergence selective herbicide metolachor to kill yellow nut grass before it emerges from the ground. Spray over the affected area and the nut grass should not sprout. Mix the product per the instructions in accordance with your particular situation. Water the product into the ground after applying so it can reach the underground tubers.
Use the selective herbicide imazaquin to control purple nut grass after it has sprouted. Spray the product over the affected area. Mix it per the instructions in accordance with your particular situation. Do not water, allowing it to stick to the leaves.
Select a nonselective herbicide in more difficult situations, where both types of nut grass are present and growing in large quantities. Use halosulfuron or glyphosate. Mix according to directions and your specific situation. Use caution, as these products can damage and kill other vegetation besides the nut grass. Spray over the affected area of the lawn and wait. You should see results in as little as 24 hours. Do not water after applying.
Spread a granular weed and feed over the lawn that specifies that it kills nut grass. This product will fertilize the lawn and at the same time kill the nut grass. Spread at a rate directed on the package, as applying too much can harm the lawn. Water the it into the lawn after applying.