A. Removing thatch that has built up in a lawn is a good idea. Thatch is the layer of decaying organic material made up of stems, roots and other material that is a normal and beneficial element of any lawn. It helps to shade roots, acts as a mulch to keep moisture in the soil and feeds the lawn as it decays. When the thatch layer gets too thick it can act as a barrier to water and fertilizer, and the lawn can actually begin to grow in the thatch, instead of the soil. If you dethatched last spring, and then cut your lawn on a regular basis, removing only about one-third of the grass blade each time, you shouldn't have to do it again this year. You may consider doing it every two or three years to keep the thatch layer from building up again.