Dethatching is essential to maintain a lush, healthy lawn. Thatch is the layer of built-up plant material between the green top growth and the roots of grass plants. Thatch develops naturally as lawn grasses grow and slough off roots, shoots and leaves. Some thatch helps protect the roots, but excessive thatch prevents moisture, oxygen and nutrients from penetrating the soil.
You can leave your grass clippings on the surface of the lawn after you mow. In order to prevent the buildup of thatch, mow frequently so the grass clippings are small and will decompose rapidly. Grass clippings contain 16 essential nutrients — including nitrogen fertilizer you’ve applied — that can be recycled back into the lawn by leaving the clippings in place.
One problem with a thick layer of thatch is that newly sown seed will root in the thatch layer — not the soil. Thatch doesn’t provide the same insulation as soil, so the roots of such plants dry out quickly, and the lawn dies. A heavily thatched lawn dries out faster so you have to water more frequently.
To determine whether your lawn has too much thatch, remove a plug of lawn, and measure the layer of thatch between the top growth and the root zone. If it measures more than 1/2″ in depth, you should dethatch the lawn. You may need to perform this chore only once every two to three years.