Thatch, built-up plant material between green growth and the grass roots, is essential, but too much can deter healthy lawn growth.
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Lawn expert Dr. Tom Samples of the University of Tennessee Agricultural Extension Service explains that 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.
There are several tools that can be used to remove the thatch layer, but contrary to popular belief, a metal spring rake isn't one of them. The tines can't penetrate the foliage to reach the surface of the soil. This type of rake is good for removing fallen leaves, but not thatch.
To remove thatch from a small lawn, use a thatching rake, which will slice into the lawn and bring up vast amounts of dead material. Rake in one direction to prevent damaging grass roots. A thatching rake costs about $30. Once you remove the thatch layer, clean the lawn with a metal leaf rake.
After getting rid of the thatch, you can compost it and recycle it back into the garden.
You can remove thatch in summer, fall and even when the lawn is dormant in winter. Dethatching isn't recommended in the spring during the transition between dormancy and active growth because at this time the energy and nutrient stores in grass roots are low.