When to Dethatch & Aerate a Lawn

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Dethatching and aerating your lawn can help to maintain the good soil and water drainage that are part of a healthy lawn. Both processes are hard on young grass, so do this in the late summer or fall.

What Is Thatch?

Thatch is a natural part of your lawn. It is comprised of the grass clippings from mowing and the leaves and twigs that fall on your yard. Your grass needs to have thatch. The problem arises when that builds up. On a healthy lawn, the thatch decomposes naturally, providing nutrients to your grass. The thatch layer should be about 1/2 inch thick. Dethatching should be done if the layer is much thicker.


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You can dethatch a small area by using a stiff rake, but it will be hard work. Two types of dethatching machines are available for rent. The best is a vertical mower. The blades of the vertical mower cut into the thatch layer and pull it away. A power rake can also be used. Power rakes can pull up grass as well as thatch if you aren't careful. One you have loosened and pulled up the thatch, you need to rake it up and remove it.

Soil Compaction

Grass roots need air. Compacted soil does not have much air in it. Compacted soil also does not drain well, leaving puddles on your lawn. High-traffic areas of your yard probably are more compacted, so getting grass to grow well can be difficult. You can test the compaction of your soil by trying to put a shovel through it. If you can easily push a sharp shovel at least halfway down, your lawn is not too compact. If it takes a lot of effort to push the shovel down, you need to aerate.



Aerating your lawn will improve the health of your grass, increase drainage and even help prevent thatch build-up. Rent a core aerator and run it across each area until you have about 30 holes per square foot. You should only need to aerate about every three years. Do not rake up the plugs of soil that the aerater creates. You may want to use a good weed treatment in the spring because aerating can bring weeds to the surface.