Lawn Dethatching 101: Why, When, and How to Do It

The process of dethatching removes organic matter that gets in the way of the flow of nutrients to your soil. When you aerate your lawn, on the other hand, you remove cores. of the soil to give roots space to grow. This process only removes small amounts of thatch and focuses on relieving soil.

What Every Homeowner Needs to Know About Dethatching Lawns

Keep your grass lush and green by dethatching it when needed. With these lawn tips, you’ll be an expert in no time.

Viveka Neveln is the Garden Editor at BHG and a degreed horticulturist with broad gardening expertise earned over 3+ decades of practice and study. She has more than 20 years of experience writing and editing for both print and digital media.

Thatch is a matted layer of grass stems, roots, stolons, rhizomes, and other organic debris that builds up faster than it can decompose. Thatch accumulates immediately below the green surface of the lawn—on top of the soil at the base of the blades. A layer of thatch less than ½ inch thick is normal and doesn’t present cause for action. In fact, a thin layer of thatch is a good thing: It reduces soil compaction and increases tolerance for cold and heat by protecting the crown (the point on the plant where grass growth originates). Thatch can also reduce water loss through evaporation.

If the thatch is more than ½ inch thick, it may cause trouble, and it may be time for dethatching a lawn. Think of it as a layer of plastic wrap on top of the soil. Your grass won’t have access to air, water, and nutrients because thatch blocks them from reaching the roots. A thick layer of thatch can harbor disease-causing insects and fungi, prolong high humidity that promotes disease, and bind or tie up pesticides. And as thatch builds, grass roots knit into the thatch layer instead of the soil, where they easily succumb to environmental stresses such as prolonged periods of hot, dry weather.

What Causes Thatch?

There are numerous causes for excessively thick thatch. The most common ones are poorly aerated soil, excess nitrogen (which leads to excessive growth), and too much water (which reduces the amount of oxygen in the soil). Thatch may also result from activities like the overzealous use of pesticides that kill the earthworms and microorganisms that break down organic matter.

Some lawn grass varieties are more prone to developing thatch than others. For example, among the cool-season grass species, Kentucky bluegrass is a prime offender for spreading aggressively and accumulating thatch. (Tall fescue may be a better choice for avoiding thatch.) Bermuda is more likely to accumulate thatch than zoysia among the warm-season grass species. (Check with your local cooperative extension service to better understand the grass species that work in your area.)

There are multiple ways to determine if your lawn has a thatch problem. The easiest is to check to see if your lawn is green on top but brown below. The best time to check is after you mow when you’ve just cut off the top green growth. If you have thatch, the lawn will look brown or dead. Another test is to walk across the lawn: If it feels spongy, it may be due to thatch.

If you’re still in doubt, use a spade or knife to cut several small plugs from the lawn. Measure the thatch, which will appear as a layer of spongy brown material between the grass and the soil. Dethatching lawns is in order if the thatch is more than ½ inch deep.

When Is the Best Time for Dethatching Lawns?

Dethatching lawns should only be done when conditions are best to promote rapid recovery of your grass type. The best time to dethatch cool-season lawns is late August to early October, depending on your location, when the grass grows vigorously and few weed seeds are likely to germinate. A light application of fertilizer (½ to ¾ pound actual nitrogen per 1,000 square feet) and regular, deep watering will speed the lawn’s recovery.

Dethatch warm-season lawns in late spring or early summer after completely greening and growing rapidly.

How Do I Dethatch My Lawn?

There are several ways of dethatching lawns. For lawns with moderate levels of thatch, aerating (more on that below) may do the trick. Or use a cavex rake (aka thatching or lawn dethatcher rake) with unusual semicircular tines. Those knifelike blades cut through the sod and pull out thatch. The most effective solution for dethatching lawns that are large and have serious thatch problems is a vertical mower (aka power rake). Resembling a heavy-duty power mower but with a series of spinning vertical knives, it cuts through thatch.

Dethatching often creates a large volume of debris that must be removed. If the debris is weed-free and you have not used herbicides or pesticides on your lawn, compost it. Or check to see if your city has a composting program for yard waste.

How Do I Reduce Future Thatch Accumulation?

Thatch is inevitable, but appropriate lawn care practices will help reduce the severity in the future. Use the right type and amount of fertilizer for normal growth. Water deeply, thoroughly, but infrequently. Maintain proper pH levels; adjust them if needed. And aerate your lawn regularly to make room for new growth.

How Do I Aerate My Lawn?

The roots of all plants need air as much as water, which is why aerating is so important. It’s a simple process of perforating the soil (and any thatch) while removing plugs of lawn that leave behind small holes that allow water, air, and fertilizer to get to roots. Aeration enables the roots to grow deeply, producing a more vigorous lawn.

Multiple tools are available for aerating lawns. If your property is small, a foot-press aerator that you push into the soil like a spade may suffice. For large lawns (more than a few hundred square feet), you may want to buy or rent an engine-powered core aerator that resembles a lawn mower. You steer it across the lawn—several times in different directions—to break up compacted soil as much as possible. (Aim for 20 to 40 holes per square foot.) Either method requires moist soil, so aerate a day or two after a soaking rain or water the lawn deeply before aerating. Soil that’s too wet or too dry will prevent the tool from working correctly.

Aerating tools remove thin, cigar-shaped plugs of soil and deposit them on the lawn’s surface. (Avoid tools that are designed to punch holes without removing cores.) Let the plugs dry for a few days, then break them up with vigorous raking to create a thin, beneficial topdressing.

The best time to aerate cool-season lawns is late August through early October. The second best time is in the spring. (Wait until you’ve mowed the lawn twice before aerating in spring.) Follow with regular, frequent watering. The best time to aerate warm-season laws is in late spring or early summer—or anytime followed by four weeks of good growing weather. Lawns with severe thatch problems may need twice-yearly aeration.

Lawn Dethatching 101: Why, When, and How to Do It

Lawn dethatching can be crucial to keeping your grass and soil healthy. Even if you are mowing and doing everything else necessary for your lawn, thatch can build up. Over-watering and over-fertilization can cause excess thatch. Detaching removes the thick layer of dead plant material (thatch). This allows air, water, and nutrients to reach your plants and soil again. Dethatching allows your lawn to drain better as well. By learning why dethatching is important, as well as when and how to dethatch, it will be easier to keep your lawn healthy. Here’s how it’s done.

What Is Thatch?

Before diving into why dethatch lawn spaces, let’s first understand what thatch is.

The term “thatch” refers to a tightly intermingled layer of dead organic matter, as well as living grass shoots, stems, and roots. This thatch layer builds up above the soil but below the green vegetation, creating a built-up area above the soil and grassroots.

While lawn dethatching is an essential aspect of lawn care, a bit of thatch is actually normal and beneficial. This is because:

• It gives a slight bounce to turf, ideal for little feet and golf balls.
• A thin layer can help boost the grass’ resilience to daily wear.
• A thin thatch layer helps insulate the soil and grass roots against extreme temperatures.

This lawn thatch develops as a result of organic matter producing faster than it decomposes in the grass. While a fast-growing lawn is ideal to many, the excessive thatch build-up can cause issues including:

• Creating a home for disease-causing fungi and insects.
• Holding humidity, which promotes disease.
• Limiting root growth, creating a shallow system of grassroots.
• Slows down the movement of air, water, and nutrients in the soil.

Common Causes of Thatch

There are many factors that can cause a thatch layer to build in your lawn. While some used to think a thick thatch was a result of grass clippings, it actually typically is built up due to various elements, including:

• Dead leaves that decayed, as well as stems and roots.
• Roots growing within the thatch layer without reaching the soil beneath.
• Lateral shoot growth which interferes with roots that are growing down.
• Infrequent mowing. It’s recommended that lawns are mowed weekly during the growing season.
• Mowing off too much at once. It’s best to follow the one-third rule, removing just one-third of the height of the grass per mow.
• Too much water, which causes the soil to become wet resulting in drainage problems. On the other hand, dry soils can create build-up when too dry, keeping water from passing through.
• Pesticides are used when they aren’t needed, ultimately killing earthworms which stimulates thatch breakdown.
• The type of grass. Cool-season grasses such as Kentucky bluegrass, creeping bentgrass, and creeping red fescue can have stem issues that contribute to thatch buildup. Additionally, warm-season grasses that create excess thatch are Bermudagrass, centipedegrass, St. Augustinegrass, and Zoysiagrass.

Signs Your Lawn Needs Dethatching

Wondering when to dethatch lawn environments? There are a few ways to tell it’s time to pull out your lawn mower and dethatch your lawn, including:

• The thatch is above a half-inch thick.
• The lawn surface feels bouncy or spongy when walking on it.
• There are noticeable dry spots, signaling the thick thatch is preventing water from reaching the soil surface.
• Footprints take more than an hour to disappear.
• The grass appears to be diseased.
• There are insect problems.
• The lawn isn’t as hardy as it was before.

When to Dethatch a Lawn

Knowing when to dethatch a lawn is essential to ensuring the best results and a healthy lawn.

While it used to be recommended that you dethatch your lawn yearly, there is now a more strategic approach to this lawn service. It’s essential that you do not dethatch your lawn too often, as the deep dethatching rake can tear at grassroots and open up your lawn grass to disease and pest problems. In addition, as previously mentioned, thinner thatch layers can be beneficial to moderating soil temperature, preserving moisture, providing nutrients, and blocking out burrowing pests.

That being said, it’s time to dethatch your lawn when the thatch builds to over 3/4-inch thick. This may only be needed every few years, but being aware of when will make a big difference in the health of your entire lawn. However, when to do this depends on if you are dealing with cool season or warm season grasses.

• Cool Season Grasses: Dethatching is best done when the lawn is growing and the soil is somewhat moist. Typically, cool-season grasses are best to dethatch in early fall or early spring. Especially with Kentucky bluegrass, which is most likely to build thatch, it will be important to monitor your grass for loose thatch.
• Warm Season Grasses: This type of grass is best dethatched when they are growing in the late spring and early summer. It’s best to dethatch these thick thatch layers after you have mowed once. Most commonly, Bermudagrass will need more frequent dethatching than other types, like zoysiagrass.

How to Dethatch a Lawn?

The easy answer on how to dethatch a lawn would be to hire a local lawn care professional. Especially if your thatch is more than 2 inches, hiring a professional might be best. A thick amount of thatch often needs more than one dethatching. If you want to do it yourself there are a few different options and tools. Before you start any of them, it is best to mow your lawn down.

Step 1: Prepare Your Lawn for Dethatching

To prepare for dethatching a lawn, we recommend:

• Dethatching when your soil is moist, but not overly soggy. To prepare your soil layer, water your lawn thoroughly two days before dethatching.
• When using a dethatching machine, mark any shallow irrigation lines, buried utility lines, or sprinkler heads before beginning the process.
• Mow your lawn to half its normal height before dethatching.
• In the case you’re renting a dethatching machine, ask the rental company to adjust the spacing and depth to your specific grass type. You should not cut deeper than 1/2 inch into the soil.

Step 2: Use the Right Tools

To properly dethatch your lawn, there are a number of tools to turn to, including a thatching rake, power rake, vertical mower, and more. Let’s break it down.

Manual Dethatching

For manual dethatching, all you need is a dethatching rake. This method is best for a small amount of thatch on a small lawn.

Power Rakes

Similar to a mower, power rakes dig into thatch at the soil and pull it out. This is also good for a small amount of thatch. You want to be careful as it can be destructive to your grass. It’s best used on strong grass that can take it.

Vertical Mowers

Vertical mowers, like power rakes, pull the thatch up from the soil. They often take grassroots along with it. Vertical mowers are good if you have a thick layer of thatch.

Regardless of what tool you choose to use, there is some aftercare that is necessary. After you finish dethatching, it is important to finish by raking up all the excess thatch on your lawn. Then water and fertilize your lawn thoroughly.

Step 3: Dethatch

Now that you’ve prepared, it’s time to remove the thatch from the grass blades. To address too much thatch, we recommend:

• Dethatching with the proper soil moisture. It’s important that the soil is moist, but now wet.
• Run the dethatching machine at least three times. Be sure to go in different directions each time to properly dethatch your lawn.
• Be sure that the machine is churning up roughly the same volume of material with each pass across the lawn.
• Always remove the piles of thatch immediately after dethatching.
• During this process, it’s best to seed the lawn right away to help fuel new growth.
• Before finishing, consider topdressing. This can help boost your existing root system for a healthier lawn.

Step 4: Don’t Forget about After Care

Don’t panic if your lawn immediately looks worse for wear. No matter what method of dethatching you used, it will take a moment for your entire lawn to look its best again. To boost the process, implement a quality fertilizer and deep watering to your lawn back on its feet and promote a vibrant, resilient finish.

Remember – the dethatching process is quite intricate and is like doing surgery on your lawn. For this reason, it takes a moment for it to recover!

Downsides of Dethatching

Thatch has many beneficial purposes. It only becomes damaging when too much builds up. The right amount of thatch protects your plants from extreme temperatures. It also keeps moisture in the soil and prevents weeds. If you can keep your thatch at a small amount, there is no need to dethatch. The problems discussed above that thatch can cause only becomes an issue when there is too much of it.

If you do need to dethatch, it is important to remember that dethatching can be damaging. Dethatching tears and rips dormant turf. This can affect its ability to recover, especially after a hard winter. Using power equipment to dethatch can bring up weeds. These weeds can then infiltrate your lawn. If you dethatch excessively, or when it is not needed, it will end up causing more harm than good.

How to Prevent Thatch Buildup

There are ways to prevent that thick thatch layer from building up between grass blades. To boost your lawn health and prevent thatch, we recommend:

• Fertilizing your lawn only enough to maintain the desired growth and color. This is best done in the fall to grow strong roots.
• Aerate the soil to promote proper drainage. In addition, fertilize a week before aerating to boost grass growth.
• Mow properly! Never trim more than one-third of the grass height, and leave the grass clippings to decompose.
• Avoid pesticides unless entirely necessary.
• Test your soil often to check the nutrient levels and acidity, ensuring you manage the pH for a healthy lawn. Keep in mind that too much fertilizer can cause an overproduction of thatch, and testing your soil can help determine if and when fertilizer is needed.

When to Call a Lawn Care Professional?

Whether your lawn is feeling abnormally bouncy, or you can actually see how much thatch has built up on our lawn, it’s time for some general thatch maintenance. With knowledge of everything from cool season lawns, to heavy clay soil, and maintenance of small lawns, our lawn care professionals are proud to offer our lawn dethatching services for a healthier lawn.

As the leading Midwest commercial landscaping contractor, our team at Earth Development can help you make your landscape look good with all types of individualized solutions for lawn cleanup, lawn fertilizing services, and more. Get a free quote online today, or contact us now at (866) 576-78171!

FAQs on Lawn Dethatching

Are some lawn grasses more prone to thatch buildup?

Yes, there are some types of grass that are more prone to excess thatch than others! For example, vigorous, spreading grasses like Bermudagrass, creeping fescues, and Kentucky bluegrass tend to need more regular dethatching. Additionally, lawns with low oil pH or compacted soil will build excess thatch, too. On the other hand, clump-forming grasses, like tall fescue to perennial ryegrass are less likely to build a thick thatch as often.

When shouldn’t you dethatch?

There are periods of time when it isn’t ideal to dethatch your lawn. For instance, temperature extremes, such as super high temperatures are not ideal to dethatch. In addition, droughts or late fall when winter is approaching isn’t a great time to dethatch, either. Typically, it’s best to dethatch during an active growth period for your grass.

What is the difference between dethatching and aerating a lawn?

The process of dethatching removes organic matter that gets in the way of the flow of nutrients to your soil. When you aerate your lawn, on the other hand, you remove cores. of the soil to give roots space to grow. This process only removes small amounts of thatch and focuses on relieving soil.

Eddy is a distinguished expert in the snow removal and landscaping industry, boasting over 20 years of experience. As an Advanced Snow Manager certified by the Snow and Ice Management Association (SIMA), he is dedicated to upholding the highest industry standards. His strong commitment to excellence and relentless pursuit of improvement makes him a trusted voice in the snow removal and landscaping.