Knowing when to dethatch your lawn is key to maintaining its health and appearance. It keeps the roots strong, prevents weeds, pests, and diseases, and helps with nutrient absorption.
Before you dethatch a cool-season, warm-season, or mixed lawn, consider your grass type’s growing season, the amount of foot traffic, and the health of your lawn. They will help you know how often to dethatch.
Why timing matters
Timing is crucial for dethatching because the process is actually quite stressful on your lawn – it involves physically pulling up dead grass and organic material, which can also damage some healthy grass in the process. Think of it like major surgery for your lawn.
When you dethatch during the proper growing season:
- Your grass has maximum energy reserves stored in its roots to recover
- Growing conditions like temperature, moisture, and daylight are optimal for new growth
- Your grass can quickly fill in any bare spots before weeds take over
- Root systems are strong enough to withstand the mechanical stress
If you dethatch at the wrong time, like during dormancy or extreme heat, you risk:
- Killing large sections of grass that won’t have the strength to recover
- Creating perfect conditions for weeds to invade
- Stressing your grass when it’s already struggling with harsh weather
- Potentially devastating your entire lawn if adverse conditions like drought or early frost follow it
My Tip: Dethatching is best done in combination with aeration and overseeding. After you remove thatch, aerate the soil to loosen compacted soil and allow air, water, and nutrients to reach the roots. Then, finish up with overseeding to replenish the lawn with new grass.
My grandfather shakes his head at people who dethatch but skip aeration and overseeding. “That’s like opening a door and never walking through it,” he said. He never cut corners, and his lawn is the softest, thickest grass I’ve ever walked on.
If dethatching, aeration, and overseeding are too much of a time suck for you, hire a local lawn care professional to get the job done without any hassle.
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The best time to dethatch warm-season grasses
Warm-season grasses thrive in hot weather, so their peak growing season is late spring to early summer when soil temperatures are consistently above 65 degrees – this is the best time to dethatch.
During this time, warm-season grasses like St. Augustinegrass, Zoysiagrass, Bermudagrass, and Bahiagrass bounce back quickly from the stress of dethatching as they receive plenty of sunlight and warmth.
Of the warm-season grasses, Zoysiagrass, St. Augustinegrass, and hybrid Bermudagrass are most susceptible to thatch buildup.
Read More: How Much Does Lawn Dethatching Cost?
The best time to dethatch cool-season grasses
Cool-season grasses like Kentucky bluegrass, perennial ryegrass, and the fescues thrive in cooler temperatures, so they grow best in fall and early spring. This is the ideal time to dethatch your cool-season lawn without stressing it too much. The cooler temperatures encourage root growth and recovery in cool-season grasses.
Of the cool-season grasses, creeping red fescue, creeping bentgrass, and Kentucky bluegrass are most susceptible to thatch buildup.
The best time to dethatch mixed lawns
Mixed lawns contain both warm-season and cool-season grasses, which means they are a bit trickier when it comes to dethatching.
The best time of year to dethatch a mixed lawn depends on the peak growing season of the dominant grass. So if your lawn has more cool-season grass than warm-season grass, dethatch in early fall or early spring; if it has more warm-season grass, dethatch in late spring or early summer.
If the lawn has an equal mix of both, dethatch in early to late spring or in early fall.
Read More: Benefits of Dethatching Your Lawn
Factors that affect how often to dethatch
Dethatching can really stress your lawn out, so only do it when necessary. Always consider these factors before deciding to dethatch:
Your grass type
Dr. Gil Landry, turf specialist at the University of Georgia Extension, says warm-season grasses are more thatch-prone than others.
Landry says that warm-season grasses tend to grow faster and contain more lignin that resists decomposition than cool-season grasses, so they form more thatch.
Likewise, you’ll also see more thatch if you’re trying to encourage dense, vigorous growth through fertilization.
“These grass clippings are larger, slower to decompose and less likely to work down into the turf,” Landry says.
Read More: An Ultimate Guide to Grass Types
The amount of foot traffic on your lawn
Frequent use of your lawn for sports and other activities can cause soil compaction and thatch to build up faster.
Compacted soil restricts air, nutrient, and water flow, weakening the root system and causing organic matter to build up on the surface rather than decomposing naturally into the ground. It also reduces microbial activity that helps break down organic matter.
The health of your lawn
Healthy lawns with balanced growth, proper soil conditions, and moderate activity require less frequent dethatching. This is because they can naturally regulate thatch buildup.
You’ll need to dethatch every two to three years, but I advise monitoring the thatch layer to determine the right timing.
The thickness of the thatch layer
A thatch layer thicker than a half inch is a pretty clear sign that it’s time to dethatch. If it’s any thinner, you might be able to hold off for another year but continue monitoring it.
Signs of excess thatch
If you spot any of these symptoms on your lawn, it might be time to dethatch:
- Your grass feels spongy when you walk on it.
- Water doesn’t penetrate the soil properly but pools on the surface.
- A lot of weeds are popping up.
- Your grass has patches or general thinning.
FAQ about when to dethatch your lawn
To assess your thatch thickness, the University of Minnesota Extension suggests cutting out a 2-inch-thick piece of lawn and measuring the thatch layer with a ruler or measuring tape. You should see three layers: the grass on top, the thatch layer in the middle, and the soil and grassroots at the bottom. Measure in several places to get an average.
Yes, you can dethatch and aerate at the same time. In fact, it’s generally preferred. Do both during peak growing season for your grass type. During this time, your grass can handle the rigors of dethatching and aeration and recover faster afterward. Always dethatch first to clear debris and expose the soil.
Read More: Can You Dethatch and Aerate at the Same Time?
A young lawn typically doesn’t have enough thatch buildup to require dethatching within the first couple of years. After two years, you can check for thatch by cutting out a small section of grass and looking closely at the space between the soil and the grass blades.
It’s best to dethatch in mild, dry, cool temperatures of between 50 and 75 degrees Fahrenheit. Mild weather reduces stress on the grass, helping it recover much faster after dethatching.
A pro can handle the heavy lifting
Dethatching can do wonders for your lawn, but it takes time and effort. If dethatching your own lawn seems overwhelming, Lawn Love can connect you with a local lawn care professional. We’ll handle the heavy lifting and give you a thriving, thatch-free lawn for the long term.
Main Photo Credit: Paul Maguire | Adobe Stock
