When Is The Best Time To Dethatch Your Lawn? (2024)

When most people think of grass, they think of the long, graceful blades that stick out of the lawn. Well, that’s only about half the story that grass has to tell. Grass also has below and at-ground level parts, like the crown, rhizomes and roots that help it stay healthy and spread horizontally across the ground. Although the grass blades, which are basically leaves, decompose easily, these other structures do not.

Over time, the other parts of your grass plants can build up into a spongy layer between the grass leaves and the soil. This is the thatch. A small amount of thatch is pretty normal for lawns, but too much and you risk creating a situation where water and oxygen have trouble penetrating to the grass’ roots, or in severe cases, roots are only anchored in thatch, making it hard for the grass to thrive and even harder to execute any on-trend landscaping ideas.

When people give advice about dethatching lawns, they generally recommend you do it based on the depth of the thatch itself. Those people often forget to explain how to determine depth. For starters, if your lawn feels springy or spongy when you walk across it, you probably need to be looking deeper into the situation. If it’s solid and doesn’t have a lot of give, you may not yet need to dethatch.

A more scientific approach requires you remove a small pie-shaped wedge of your lawn. You should cut about two inches into the ground, and remove a piece large enough that you can make out the various structures, but not so big as to leave a major mark. You can always stick the wedge back into the hole if you’re good at puzzles.

When the wedge is exhumed, look at the layer between the grass blades and the soil. It will have a slightly different color and texture than either, so it should be pretty obvious where the thatch is. You can measure it with a tape measure or ruler, just be sure to measure at several points across the sample for the most accurate results.

If the thatch layer is more than a half-inch thick, you should definitely be thinking about dethatching. If it’s thicker than that, you should be actively doing so. But, timing your dethatching is also pretty important if you want your lawn to be at its best.

Because dethatching is basically very intensive, deep raking, the grass on your lawn will be damaged no matter how careful you are. If you plan your dethatching when the grass is growing vigorously, it will recover much faster than if you try this move when it’s dormant. So, ideally, early spring or when it starts to cool in the late summer are great times for dethatching.

Don’t fertilize before you dethatch, as much of the fertilizer will be broken up, removed and wasted. Instead, fertilize after dethatching in order to give your grass a little pick me up after such a harrowing experience, then water thoroughly so that the fertilizer gets to where it needs to be sooner.

For lawns with excessive thatch, or that have never been dethatched before, you may want to do this process in phases. Removing a bit of thatch by passing over the lawn two or three times in different directions, letting the lawn recover and then doing it again, is a much better solution than simply going for broke and trying to accomplish this all at once.

This is a trick question.

To avoid hiring a landscaping professional, your lawn should be dethatched whenever necessary, which will vary widely between grass types, the care your lawn receives and local conditions. A few factors that will encourage thatch to accumulate include having fast-growing grasses, mowing infrequently or having your deck set above two inches as well as growing grass on chronically wet or dry soils or in acidic soils or over fertilizing your lawn.

Assuming an average growing grass and average care, you can expect to need to dethatch your lawn once a year or once every two years. Just check the thatch depth when you feel like it may be getting close to time, and if there’s more than a half inch of accumulation, spend a weekend working on the lawn. It’s better to check and be wrong than to not check and have a serious thatch build-up.

If you’re currently panicking because you never considered dethatching your lawn, you may live in an area where tall fescue or perennial ryegrass are common. They rarely need dethatching because of their growing habits, so take a breath and go find a friend with some troublesome zoysiagrass to help instead.