When to Dethatch a Lawn?

Thatch, a layer of dead grass and organic debris just below the surface of a lawn, can cause problems when it becomes extensive. When your lawn has too much thatch, water, air and vital nutrients cannot reach the roots of your grass. The time of year you de-thatch your lawn is a key part of performing this task successfully.

Time of Year

Early autumn is the best time to remove lawn thatch, according to the Ohio State University Extension. Removal at this times give the lawn time to recover from the de-thatching process before the next growing season. A cool time of year is generally less stressful on your lawn than warmer temperatures. If removal in early fall is not possible, very early spring is the next best time to de-thatch.

Check Lawn

You need to check your lawn regularly for excessive thatch. When a thatch layer grows close to 1/2 inch thick, it is time to take action. Waiting until the layer is 1/2 inch thick or more increases the difficulty of removal. To check your lawn for thatch, dig out several plugs at depth of 2 to 3 inches. Thatch will show itself as a layer of brown spongy organic material.

Removal

You can remove thatch in various ways. Perhaps the simplest method is to use a special rake with tines that dig into the thatch layer. This method works well for small lawns. For larger yards, a machine called a power rake can work well. You can rent a power rake at many garden centers or equipment rental stores. The best method of removal, according to the Ohio State University Extension, is core aeration. This process removes 2- to 3-inch-long plugs from the lawn and lets them decompose back into the turf.

Prevention

Prevention is the best method of controlling thatch build-up. Proper mowing techniques will decrease the chances of accumulation. Cut your grass at the recommended height with a mulching, says the University of Missouri Extension. Avoid cutting more than 1/3 of the grass blade. You can leave the clippings on the lawn to decompose if no thatch is present. Remove any build-up of excessive clippings. Although grass clippings do not cause thatch, they can accelerate its growth once a layer begins. Collect the clippings if you determine that thatch is already present in your lawn.

References

• Ohio State Univesity Extension; Thatch: The Accumulation in Lawns; William E. Pound, et al.
• University of Missouri Extension; Thatch: Enemy of Lawns; Brad S. Fresenburg; April 2010
• This Old House; How to De-thatch a Lawn; Roger Cook