Thatch is the layer of slowly decomposing grass stems, roots, clippings and debris that accumulate at the soil surface over time. It can build up in your lawn and virtually choke it to death. Excessive thatch buildup is commonly found in lawns that have been overfertilized or overwatered and have never been aerated. Thatch buildup of 3/4 inches or more will restrict water and nutrient penetration into the soil (think of a thatched roof) and can harbor disease organisms that can increase the need for pesticides. Slice open a section of turf. If the thatch is more than 3/4 inches thick, take action. Regular core aeration will slow thatch development. However, it won’t do much to remove existing thatch. This can be done by renting a power rake, which will ‘lift’ the thatch from the soil surface. This thatch residue can then be raked by hand and removed. Dethatching is hard work, so it’s smart to prevent buildup in the first place. The best way to do that is to avoid overwatering and overfertilizing.