Thatch is the accumulation of dead plant material on a lawn. Contrary to popular belief, cut grass is not the main component of thatch. Grass decomposes easily due to its high composition of water. Thatch is dead and living plant roots, crowns, and shoots according to University of Missouri Extension. Although a thin layer of thatch is OK, a layer thicker than 1/2 inch may cause grass problems. Excessive thatch reduces water absorption, harbors disease and may cause dry patches.
Dig up two or three samples from the lawn using a knife and determine whether the thatch is deeper than 1/2 inch. Thatch that is thin does not need removal.
Run an aerifier over the lawn several times to remove plugs of dirt from the lawn and increase drainage and air movement. An aerifier core mulcher removes 3- to 4-inch plugs of dirt from the lawn and loosens thatch for vertical mowing. Run the aerifier in a north to south direction, the east to west for the best coverage.
Set the tines of the vertical mower at a depth that brings up a small amount of dirt along with thatch. Test a small area of the lawn before doing longer passes to check the height.
Run the vertical mower over the lawn like the aerifier. Rake debris from the vertical mowing and add it to your compost pile.
Apply 1/2 to 3/4 lbs. of nitrogen per 1,000 square feet to the yard after dethatching to reduce recovery time.