Most homeowners should dethatch their lawn once per year. But, the frequency with which you dethatch will depend on a variety of factors, which we'll cover in this article.
It's important to understand that dethatching when it's not actually necessary can harm your lawn. So it's essential to know what to look for before dethatching.
How Often Should I Dethatch My Lawn?
You should only dethatch your lawn when it's necessary. For many homeowners, that's usually one time per year. Also be sure not to dethatch an overly wet lawn, or after it rains.
How Do I Know If My Lawn Needs Dethatching?
If the layer of thatch material is greater than 1-inch thick, then you know it's time to dethatch your lawn.
If your lawn has too much thatch, it will feel spongy when you touch it and will scalp when you mow it. It's best to measure thatch thickness to be sure, though.
You can measure this by taking a shovel, and chunking out a piece of soil from your lawn, like in the picture above. Do this in a few different places to get a good sample.
Then, you can take a measuring tape and measure the layer of the thatch material.
If it's less than 0.5 inches, then you definitely do not to dethatch. In fact, dethatching at this level can damage your lawn (more on this below).
If the thatch layer is between 0.5 inches and 1 inch, then you should probably dethatch, but it's more of a judgment call.
Anything greater than 1 inch, however, and you should definitely dethatch.
Why Is Dethatching Necessary?
While thatch provides food sources for organic matter to incorporate into the soil, having too much thatch can become a breeding ground for diseases and pests and can interfere with helpful nutrients getting into the soil.
There are several benefits to dethatching.
Removing thatch can increase the amount of water and fertilization getting into your lawn. The dethatching process allows air, water, and fertilizer to penetrate the soil more easily, promoting healthy lawn growth, which in turns makes your grass look that much better. You can see our full list of the pros and cons of dethatching.
After you're done dethatching, you can either compost it, or throw it away.
What Month Should You Dethatch Your Lawn?
The best time to dethatch is when the lawn is growing most actively.
This is going to depend on the type of grass that you have!
For cool-season grasses (Kentucky bluegrass, perennial ryegrass, fine fescue, tall fescue) that's usually going to be either early spring or early fall.
For warm-season grasses (bahia grass, bermuda grass, centipede grass, St. Augustine grass, and zoysia grass), that's typically end-of-spring through the beginning of summer.
Can Dethatching Hurt Your Lawn?
If you dethatch too much, or when it's not necessary, then it can hurt your lawn.
This is because dethatching is a process that involves a deep, hard raking motion that can dig deep into your lawn. If it digs too deep, it can end up tearing out grass roots and expose your soil to losing too much moisture.
Also remember that "just enough" thatch does have its benefits because it decreases soil compaction and acts as a mulch to slow the loss of water from the soil surface.
So, if you dethatch too early—or too much—you are depriving your lawn of these benefits.
Along the same lines, it's also possible that your lawn still looks bad after dethatching. If that's the case, you'll have to investigate into the possible reasons why.
What's The Best Way To Dethatch Your Lawn?
The best ways to dethatch your lawn is either with a dethatching rake, or with an electric dethatching machine.
A dethatching rake (like the Groundskeeper II) really gets in and hooks onto all the twigs, debris, and ticks in your yard, without much downward pressure required on your end. The tines do a great job of cutting through the grass and really grabbing all the stuff you want to remove. That said, it's still very much a manual process and we only recommend it on smaller yards, with thinner thatch problems.
For bigger thatch problems—and bigger yards—we recommend an electric dethatching machine like the Greenworks 10. You push the machine much like you would a push mower, the electric dethatcher works by rotating tines into your lawn to pull up the thatch. For less than $150, it's a great tool to have in your lawn care arsenal.
We don't recommend using a regular rake for dethatching or a dethatching blade mower attachment because they're not powerful enough tools for the job. And a verticutting machine is overkill for most homeowners, as is a power rake and scarifier.