THATCH

Thatch is a natural part of lawns. Thatch is a buildup of grass stems, rhizomes, roots and other organic debris that decomposes more slowly than it builds up. Grass clippings and grass blades do NOT contribute significantly to the thatch layer. The thatch layer is noted by the red parentheses in the photo.

A thatch layer of up to a half inch is healthy and beneficial for the lawn. Thatch shades the soil in summer and helps protect the grass plants during cold weather. It also reduces compaction and helps conserve moisture in the soil.

A thatch layer over half an inch can cause problems. A thick layer of thatch acts like an umbrella, preventing water, air, control products and nutrients from reaching the roots of the grass. Thatch can also be a breeding ground for insects and disease by holding in humidity and preventing insect controls from reaching the soil. As the thatch builds up grass roots begin to grow into the thatch. These shallow roots are prone to drought stress more than roots that are growing into the soil.

Some grass varieties are more prone to thatch build-up than others. In our area, Fine fescue is the most prone and Kentucky blue can also be problematic. There is a solution, core aeration punches holes in the thatch bringing beneficial microbes to the soil surface to help break down the thatch layer and allow air water and fertilizer to penetrate into the soil. In some cases, it is recommended that aeration be performed spring and fall. We do not recommend dethatching. Dethatching does not remove enough of the thatch to benefit the lawn and can do more damage than good and stress the grass plants out.