When, Why, and How to Dethatch a Lawn
You cut, fertilize, and water your lawn but it’s hardly the lush, verdant carpet you imagine. Thatch buildup might be what keeps you from realizing your turf dreams.
Of all the plants, trees, and shrubs in your landscape, the lawn is the most demanding feature, requiring constant maintenance throughout the growing season to look its best. So when it doesn’t, despite your best efforts, you need to look a little deeper. Literally. Thatch, which comprises living and dead material, accumulates naturally at the base of grass where the blades meet the soil. Mulched leaves and short grass clippings tend to decompose quickly. The problem occurs when the buildup of these materials outpaces decomposition and the thatch layer thickens. The thicker the layer, the more difficult it becomes for water, nutrients, and air to reach grass roots. When this happens, the lawn suffers and it’s time to dethatch.
How to dethatch a lawn depends on the size of your landscape and how much work you’re up for.
You have three options:
- Dethatching Rake: Using the same motion you would to rake leaves, the short tines and curved blades of a dethatching rake (such as this AMES model, available on Amazon) can dig into your lawn to pull up the thatch layer. They’re great for smaller lawns and those with mild thatch buildup.
- Power Rakes: The power version of a dethatching rake (such as this Greenworks corded dethatcher, available on Amazon) is pushed much like a lawn mower. But, instead of blades, a power rake has rotating tines that dig into thatch and lift it out as you push.
- Vertical Mower: Lawns with thick thatch or those in need of total renovation would benefit from this aggressive approach. Vertical blades on a mower or scarifier (such as this Sun Joe model, available on Amazon) penetrate the thatch layer and the soil to lift the thatch—and plenty of grass roots—out.
Look for these signs to know if it’s time to dethatch the lawn.
Thin blades, weak growth, and pale color are telltale signs that your grass is struggling. But to know if thatch is the culprit, you’ll have to do some digging. Use a sharp trowel or spade to dig up a small section of grass. You’ll likely see a layer of brown matter where the soil meets the base of the grass blades. That’s thatch, and it’s totally normal. But if the thatch layer is more than an inch thick, it’s preventing much-needed water and nutrients from reaching the roots. Additionally, lawns with a thick thatch layer might feel spongy underfoot or be difficult to penetrate with your finger as you try to reach the soil surface.
Dethatching is not a yearly chore.
Unlike mowing the lawn, dethatching is not a regular lawn chore. Instead, it’s something you might do every two to three years, depending on the type of grass and your growing conditions. Some fast-growing grasses like St. Augustine grass and Kentucky bluegrass are more prone to thatch than other varieties, especially when grown in compacted or heavy clay soil. Timing should coincide with your lawn’s peak growth period and varies based on the type of grass you have. Dethatching is stressful, so doing it when your lawn is at its strongest during the year will aid its recovery. Early spring and early fall are ideal times for cool-season grasses like Kentucky bluegrass and perennial ryegrass. Your cue to dethatch warm-season varieties like zoysia and Bermuda grass occurs in spring or early summer after they’ve completely “greened up.” If your lawn is dormant or stressed by drought, don’t dethatch. You can do irreparable damage.
The lawn will grow stronger without a thatch barrier.
Allowed to grow unchecked, thatch forms an impenetrable barrier that prevents water, air, and nutrients from reaching roots. A thatch layer of an inch or more is a breeding ground for fungal diseases and mosquitoes that favor humid, wet conditions where water can’t percolate into the soil. What’s more, grass roots become snarled in thick thatch instead of knitting into the soil, making them vulnerable to damage in prolonged periods of hot, dry weather. Dethatching, while necessary and beneficial to the lawn, often can leave it looking anything but lush. With the new real estate available, grass roots will spread and fill in the bare spots. It’s also a great time to spread grass seed.
When the time comes, follow this process for how to dethatch your lawn.
For small lawns, use a dethatching rake to work across the lawn using the same motion you would when raking leaves. Not only will you be helping your lawn, you’ll get a workout too. Power rakes, available for rent at many home improvement and hardware stores, are ideal for larger spaces and operate like a lawn mower. As you push it back and forth across the lawn, the rake lifts thatch and deposits it on top of the grass. Either method leaves a significant amount of debris behind.
Then, you have a few options for its disposal:
- Bag it as yard waste for your next garbage pickup.
- Call your municipality to see if they have a composting program.
- Compost it for your garden. Avoid this option if your lawn is chemically treated or full of weeds at the time of dethatching.