Thatch is the layer of decomposing debris that naturally accumulates over time, which can be found on top of the soil below the grass line in your lawn. Some species of turf grass such as Kentucky bluegrass, a favorite here in Colorado, naturally produce more thatch. Contrary to popular belief, leaving grass clippings after mowing does not contribute to the development of thatch. Clippings are mostly water and decompose rapidly, leaving behind beneficial nutrients for the lawn. A certain amount of thatch is normal and is not detrimental to maintaining lawn health; some thatch can even help with resiliency in high traffic areas. Once the thatch becomes more prevalent, however, it can cause problems. An excess of thatch in your lawn will cause it to shed water, thus restricting the absorption of water and nutrients into the soil and resulting in an increased susceptibility to fungi, insects and drought. We recommend power raking once you reach about 1/2 to 1 inch of thatch. When thatch dries out, it becomes really difficult to rewet. Dry thatch becomes a barrier to water and fertilizers, causing the turf grass to become dry and stressed. In Colorado, the predominant insect problem with mites. Mites really love drought stressed lawns and dry thatch becomes a great hiding place for them to multiply and feast on your thatch and your lawn.