What is thatch?
Thatch is the layer of dead and living plant material that forms between the soil surface and green vegetation. It is composed of shoots, crowns, and roots. Thatch, to some degree, is present in all lawns. However, when thatch is present in amounts greater than ½ inch, it is usually detrimental. Excessive amounts of thatch increase the potential for turf damage due to drought, extremes in temperature, diseases, and insects. The potential for damage increases because the turfgrass roots are actually growing in the thatch layer rather than in the soil.
Several factors promote thatch development. Heavy nitrogen fertilization, excessive irrigation, and infrequent mowing are the main contributors of thatch.