Nut grass, also called nutsedge, is a horrifically resilient weed that plagues many a lawn. It has strong roots and nodules that are often referred to as "nuts" (hence the name). The most thorough way to rid your lawn of nut grass is by removing the plant, root and all, by hand.
How do I get rid of nut grass in my lawn?
The best way to remove it is by digging it out with a small spade. You have to be extremely diligent with this to ensure there is no roots or bulbs left in the soil as Nutgrass will reappear if left behind.
Is nutsedge bad for your lawn?
Damage to Lawns
Nutsedges are a problem in lawns because they grow faster, have a more upright growth habit, and are a lighter green color than most grass species. These features result in a nonuniform turf.