A little thatch is good for every lawn as the dead grass will break down and become organic fertilizer. When dead grass, stems and roots build up to a level of over 2 inches, however, they form a mat that can hinder moisture and nutrients from nourishing the lawn. A buildup of dead grass can also be home to insects and disease.
When excessive thatch occurs, it can be removed with a vertical mower or dethatcher, but this is only a temporary fix, and the thatch can return if the cause of the buildup is not corrected. Environmental factors that favor the buildup of thatch include wet, heavy soil, soils with high pH (alkaline) or compacted soil.
Using a Power Dethatcher to Dethatch Your Lawn
Calibrate the blades of the power dethatcher. The people at the rental center can advise you on the procedure. Numerous blades, vertically aligned, cut to the surface of the lawn and sometime down into the soil. The blades must be calibrated depending of the type of grass in the lawn. The blade depth is usually set to cut about one-half inch into the soil so that the surface of the soil is scratched as the thatch is removed. Warm season grasses need a blade spacing of 1 to 2 inches, while delicate, thinner grasses will be spaced at 3 inches and the height should be raised as well.
Start the power dethatcher and push across area of lawn needing maintenance.
Make a second pass, in a crossing pattern, to assure complete dethatching.
Rake the area and dispose of the debris.
Distribute new grass seed in thin and bare spots of the lawn. After dethatching with a power dethatcher, the lawn may exhibit bald patches and, depending how deep the blades have cut, the stress put on the lawn may require quite a bit of recovery time.
Gently rake the newly seeded area so that any suspended seed is deposited into the soil.
Add fertilizer to the area.
Cover the re-seeded areas with organic matter or sand.
Water the stressed lawn more frequently than you would a healthy lawn to aid recovery.