Thatch is the accumulation of rotting organic matter, such as grass clippings and leaves, at the bottom of your lawn. It is easily identified when the bottom of the grass looks rotted and brown while the top is still green. Thatch can be removed with a dethatcher or power rake which makes vertical cuts into the ground to bring the rotted debris up to the surface for easy removal. However, before dethatching becomes necessary or after dethatching your lawn, it’s time to start preventing thatch with a few good lawn care practices.
Mow your grass at its recommended height to help prevent thatch. Most grasses should be kept at a height of 2 to 3 inches. Cut grass at the lowest recommended height during the spring and fall and at the highest recommended rate in the summer. Always avoid cutting more than 1/3 of your grass’s current height. For example, cut no more than 1 inch off of grass that is 3 inches high.
Attach a mulcher to your mower or rake the clippings after mowing if you cut more than 1/3 of the grass's height at any given time. Too much clippings take longer to properly decompose and can therefore cause thatch.
Avoid fertilizing your lawn too much, especially fertilizers high in nitrogen. Buy fertilizer that is labeled for your particular grass and never apply more than the recommended rates as listed on the label. Too much fertilizer results in grass and weeds that grow at faster rates than they can properly decompose, which causes thatch.
Water your grass less frequently with deeper waterings rather than more frequently with shallow waterings. Shallow waterings only helps the weeds grow and not the grass, since most grasses have deeper roots than weeds. Water grass once or twice a week with 1 inch of water, and only when rainfall has not met this need and the grass shows signs of lack of water.
Limit the use of pesticides, if possible. Pesticides may inadvertently kill earthworms and other microorganisms that help decompose clippings and other debris that cause thatch.