Maybe you see that question and think to yourself, “Wait, I have to dethatch my lawn?” or even, “What the heck is dethatching?” Good questions! Let’s start there.
Thatch is the dense layer of living and dead plant material that can build up over time between turfgrass and the underlying soil surface. If it gets thick enough, thatch can prevent water, air, and nutrients from reaching your lawn’s root system. Thatch also creates a haven for grubs, cinch bugs, and other pests.
Dethatching, as you can probably now guess, is the process of removing this layer of decaying matter so that your lawn can breathe throughout the growing season.
How often, and when, should I dethatch?
In most cases, an annual dethatching is enough to keep a lawn healthy. Early fall is generally considered an ideal time, since dethatching should be done when the lawn is actively growing and able to withstand the aggressive scraping involved in the process. (Spring works too, but the open spaces in the lawn that result from dethatching are an invitation for crabgrass and other weeds.)
It's worth noting that a moderate layer of thatch (less than ¾ of an inch) will benefit the lawn by acting as an insulator against extreme temperatures; the cushion also reduces soil compaction in lawn’s that get a lot of foot traffic. Those are more reasons why dethatching the lawn just once a year is usually enough.
How to dethatch the lawn
For small lawns, our experts in the Home Improvement & Outdoor Lab at the Good Housekeeping Institute recommend a dethatching rake. The manual tool works like a regular rake, with tines that are strong enough to pull the thatch away from the soil. For best results, reach for the dethatching rake right after you mow the lawn, so you don’t end up with long blades of grass getting stuck in the tines.
Sun Joe Lawn Dethatcher & Scarifier
THE GROUNDSKEEPER II Dethatching Rake
If your lawn is more than a 1/4 acre, it’s worth renting or buying a mechanical dethatcher. Our roundup of best dethatchers includes several battery-powered machines that look and function much like a walk-behind lawn mower. Some of them perform other tasks, like aerating and scarifying the lawn — treatments that can also improve its overall health.
How to prevent thatch from coming back
To prevent too much thatch from forming on your lawn, avoid overwatering, as this will impede the breakdown of organic material. A single inch of water per week is sufficient, ideally delivered in one long soaking, rather than short daily sips, which leads to shallow root systems that eventually end up as thatch.
As noted above, aerating the lawn is another beneficial treatment, ideally done in the fall. Heavy-duty core aerators, available for rent from home centers, break up thatch by pulling small plugs of soil from the ground. The process also allows more air, water, and nutrients to penetrate the lawn's root system.
Remember that earthworms are a natural source of aeration that work better than any machine. They don’t like soil that’s too acidic, so you may need to add a layer of lime to bring the pH level up to between 6 and 7 on the 0 to 14 pH scale. This will also encourage the natural breakdown of organic matter by bacteria, fungi, and other microorganisms.
Having written thousands of product reviews and how-to articles on all aspects of home ownership, from routine maintenance to major renovations, Dan (he/him) brings more than 20 years of industry experience to his role as the director of the Home Improvement & Outdoor Lab at the Good Housekeeping Institute. A one-time roofer and a serial remodeler, Dan can often be found keeping house at his restored Brooklyn brownstone, where he lives with his wife and kids.
