Dethatching may sound like a mind-control scheme straight out of a dystopian thriller, but it’s a little less exciting than that: It’s a process you perform on your lawn to help your grass grow green and healthy. If your lawn is starting to develop its own spongy, brown carpet, it may be time for a thorough dethatching.
Sure, dethatching may be less enthralling than Ray Bradbury or George Orwell, but it’ll prevent fungus and disease and keep your grass healthy. Even Big Brother would have to approve.
- What is lawn dethatching?
- Benefits of dethatching
- Does my lawn need dethatching?
- When to dethatch your lawn
- How to dethatch your lawn
- What causes excess thatch?
- A little thatch goes a long way
- The problem with thatch
- Tips to prevent dethatching in the future
- Attacking thatch, by yourself or with backup
What is lawn dethatching?
Dethatching is an efficient method of removing excess thatch (the layer of debris, dead grass, and other organic matter that lies in between grass blades and the soil’s surface) from your lawn so that nutrients, air, and water can reach the soil. Basically, dethatching is a powerful, deep lawn raking.
If your grass isn’t looking as green and dense as it used to, or if it’s increasingly susceptible to dry spots and diseases, it may be crying out for a thorough dethatching.
Benefits of dethatching
Dethatching is an excellent solution for lawns with excessive thatch buildup. Choosing to dethatch your lawn will:
- Give grass roots access to nutrients, water, and air
- Improve soil health and nutrient density
- Expose lower grass shoots to more sunlight
- Improve grass health and curb appeal
- Increase root strength and depth and encourage root growth
- Reduce susceptibility to disease, fungus, and pests
- Improve the effectiveness of fertilizer
- Reduce the potential for mower scalping
- Save water
- Control weeds
- Decrease stormwater runoff
- Reduce puddling and standing water
- Help winterize your lawn and prepare it for spring success
Does my lawn need dethatching?
You can determine if your lawn needs dethatching by digging out a small slice of turf and measuring the thatch layer. It’s like checking out the layers of a chocolate birthday cake (with green icing).
Test the thickness of your thatch
To determine the thickness of your thatch:
- Use a shovel to remove a small, 3-inch-deep sample of your lawn.
- Measure the brown, spongy layer between the grass blades and the soil surface.
- If the brown, spongy layer is over half an inch thick, your lawn could use dethatching.
You also can use your finger, a stick, or a ruler to press into the thatch layer. If your finger can extend into the thatch layer by more than half an inch, it’s time to dethatch.
Signs your lawn needs dethatching
You don’t just have to rely on a dethatching test. Your lawn will let you know if it needs a strong dethatching to get back into shape. Your lawn may need to be dethatched if:
- The ground is spongy and springy to the touch
- Your grass blades are weak
- Your grass is thinning and dry spots are appearing
- Weeds are invading
- Your grass is losing its healthy, green color
- You’re developing an insect problem
- Your lawn is more sensitive to temperature extremes
- Fungal diseases are infecting your lawn
When to dethatch your lawn
What time of year should I dethatch?
Dethatch during your grass’s growing season to keep lawn stress to a minimum.
- For cool-season grasses (grown in the northern parts of the U.S.) like Kentucky bluegrass and creeping red fescue, dethatch your lawn in early spring or late summer to early fall.
- For warm-season grasses (grown in the southern parts of the U.S.) like Zoysia and bermudagrass, dethatch your lawn in late spring to early summer.
Always avoid dethatching when your lawn is dormant or stressed. Make sure you don’t dethatch in the peak of summer heat or during a drought, as this can severely damage your lawn.
How often should I dethatch?
When it comes to a lawn care schedule, dethatching isn’t like aeration (removing plugs of soil from your lawn to decrease compaction): Lawn aeration is proactive and preventative, so you’ll need to aerate annually as part of a healthy lawn routine, whereas dethatching is a solution to a problem, so you’ll only need to do it if thatch becomes an issue.
With proper lawn care maintenance and grass seed that isn’t prone to thatch, you may only need to dethatch your lawn every few years. As long as the thatch layer stays thin, nutrients can reach the soil and grass grows heartily. The problems begin when thatch grows to more than a half-inch thick.
How to dethatch your lawn
When choosing a dethatcher, you have four main options. Luckily, none of them have hypnotic voices or make you wear spiky metal headgear.
How you dethatch will depend on which device you choose. No matter the method, you’ll want to mow your grass a bit lower than normal (to about half its regular height) before you dethatch.
- Manual dethatchers (also known as thatch rakes) are rakes with short, curved blades designed to slash into your thatch and pull it up. They’re the least expensive of the dethatching options but also the most labor-intensive.
- Manual dethatchers have different blade angle settings, so you can choose how deeply the rake penetrates your lawn (depending on your thatch depth).
- Use a manual dethatcher like you would a normal rake, but dig deep into the grass with the blades. Then, pull the rake upward to loosen and remove thatch.
Best for: Small lawns with a mild thatch problem (one half to an inch of thatch buildup).
- Electric (corded) dethatchers look like miniature lawn mowers, with spiny rotating tines that can be set to different levels.
- Use a corded dethatcher like a lawn mower, making two to three passes across your yard in different directions. Your lawn will look like a grassy checkerboard.
Best for: Medium lawns with a mild to medium thatch problem.
- Power rakes are similar to lawn mowers, with steel, knife-like tines (flail blades) that rotate on the bottom of the machine, perpendicular to the ground.
- Make two or three passes (perpendicular to each other) across your lawn to dethatch the area thoroughly.
- Set the blades at the highest level first to ensure you don’t accidentally damage your lawn on your first pass.
- It’s important not to scalp your grass. Check to make sure you’re not tearing out the roots as you go.
Best for: Larger areas with a serious thatch problem and dense grass that can withstand tougher treatment.
- Vertical mowers (also known as verticutters) have flat, vertical discs that slice down through the thatch and into the soil, creating grooves. Vertical mowers dig deep, uprooting thatch to give roots an extra dose of nutrients from the soil surface.
Best for: Large lawns with a serious thatch problem that could benefit from overseeding.
Pro Tip: To prevent severe grass damage, only vertically mow centipedegrass and St. Augustinegrass once, in one direction only.
After you’re done dethatching, rake up the debris and compost it.
It’s normal for your lawn to look pretty shaggy after dethatching. This isn’t the gentlest process for your grass, so give it some well-deserved TLC: Fertilize and water your lawn after dethatching. It’s also a great idea to overseed, giving your lawn some new green growth.
Pro Tip: If you’re not overseeding, apply a pre-emergent herbicide after dethatching.
What causes excess thatch?
Thatch is made up of dead grass, lawn debris, and other organic matter. It’s natural for some thatch to accumulate, but in a healthy lawn, microbes decompose thatch at the same rate as grass shoots are produced, so thatch production and decomposition are balanced.
High levels of thatch accumulating over a short period of time is a sign you need to make some changes to your lawn-care regimen.
Your lawn may have excess thatch due to …
- Overwatering and frequent watering
- Too much nitrogen fertilizer
- Poor subsoil quality beneath the sod
- Absence of earthworms due to pesticide applications
- Infrequent mowings of tall grass (cutting more than one-third of the grass height)
- High levels of soil compaction from foot traffic or home construction
- Nutrient-poor soil with a high clay or sand content
- Acidic soil with a low level of beneficial microbes
A little thatch goes a long way
Thatch isn’t always a lawn menace: A thin layer of thatch (less than half an inch thick) is healthy for your lawn.
Benefits of thatch in moderation
1. Thatch acts as a natural mulch, keeping your soil moist and providing insulation during extreme temperature fluctuations.
2. It’s great for play: A little thatch gives you traction when you’re walking or running and softens the impact of your feet on the soil. Lawns with a bit of thatch won’t get compacted as easily as thatch-free lawns.
3. Thatch improves soil quality by acting as a food source for beneficial bacteria.
4. It gives soil a nutrient boost: Earthworms incorporate organic matter from thatch into the soil, increasing soil’s nutrient density.
5. Thatch naturally filters rainwater, straining out contaminants for cleaner groundwater and aquifers.
The problem with thatch
When more than half an inch of thatch accumulates on your lawn, thatch whirls into its villain cloak and begins plotting lawn domination. Thick thatch can be a serious lawn health problem.
When thatch is over half an inch thick:
- Soil and grass roots can’t access the nutrients they need. Excess thatch acts as a barrier to water, oxygen, and nutrients.
- Grass is more susceptible to fungal diseases. Leaf spot melting-out, stripe smut, and summer patch are especially common in lawns with excessive thatch accumulation.
- Grass is more vulnerable to pest problems. Thick thatch is a breeding ground for harmful insects and disease-causing organisms. Plus, thatch binds up pesticides so they are less effective at reaching their intended targets.
- Mower scalping is more likely to occur. Lawn mower wheels sink into the thatch, giving your grass a much shorter cut than planned. The scalping weakens grass, causing lawn thinning and weed invasions.
- Roots grow shallowly, and many roots grow into the thatch. When thatch dries out or heats up, roots in the thatch wither, desiccate, and die.
- Wet thatch acts like a wall, preventing oxygen from reaching roots. Heavy moisture also increases the risk of lawn disease and fungus.
Grass types and thatch
Your lawn’s susceptibility to thatch also depends on your grass species.
- For cool-season grasses, perennial ryegrass and tall fescue are much less likely to develop thatch than Kentucky bluegrass, creeping red fescue, and creeping bentgrass.
- For warm-season grasses, Zoysia and bermudagrass are especially prone to developing thatch.
Tips to prevent dethatching in the future
We’ll say it: Dethatching is a pain. It’s a sweaty, muscle-heavy chore that eats into the time you could be spending with friends and family. Fortunately, with the right lawn care practices, you may hardly ever need to dethatch again.
- Avoid frequent, shallow waterings. Instead, water your lawn deeply (1 to 1.5 inches) once a week or divide it into two waterings per week.
- Avoid overfertilizing, especially with fertilizer that is high in nitrogen. One or two fertilizations per year should be enough to keep your lawn green.
- Stay away from chemicals that harm earthworms: Some pesticides and fungicides can severely damage the earthworm population.
- Mow regularly, following the one-third rule: Don’t cut your grass shorter than one-third of its height at each mow.
- Test your soil every three to five years. Check with your cooperative extension service about local labs that will analyze your soil.
Avoid insecticides with carbaryl, chlorpyrifos, fenvalerate, guthion, methomyl, nicotine, and propoxur. You’ll also want to avoid fungicides with benomyl and captan. These chemicals are highly toxic to earthworms.
Absolutely. Dethatching and aerating help your lawn in similar ways, but they provide different benefits. Dethatching rakes up the mat of organic matter that impedes the flow of nutrients, whereas aeration removes cores of soil to relieve soil compaction and gives roots space to grow.
If your soil is not compacted but has a thick layer of thatch, you may only need to dethatch and not aerate. Likewise, if your soil is compacted but you don’t have a thick layer of thatch, you may only need to aerate and not dethatch.
If your lawn has both compacted soil and a thick layer of thatch, you’ll want to aerate and dethatch.
Dethatch before you aerate to remove surface debris. Dethatching will open up the soil, making aeration more effective for your lawn and less strenuous for you.
No, the idea that grass clippings cause thatch all by themselves is a myth. Homeowners shouldn’t worry about removing grass clippings on healthy lawns. Grass clippings do wonders for your lawn’s nutrient levels, quickly decomposing for the benefit of earthworms and microorganisms that maintain soil health.
The one exception? Grass clippings that are over an inch long can shade or smother the grass underneath it. In this case, you should go ahead and bag the clippings. Don’t toss them in the garbage, though. Take the eco-friendly route and use them as garden mulch or compost.
Rather than avoiding grass clippings, you’ll want to change your lawn care practices as we discuss in the “Tips to prevent dethatching in the future” section.
Attacking thatch, by yourself or with backup
As any sci-fi novel will tell you, standing up to a power-hungry villain is not for the faint of heart, and thatch sure is hungry for lawn control. If you’re ready to save your yard, dethatching is a worthy DIY project and combined with healthy lawn practices, you won’t have to do it often.
If you’d rather let an expert mount the resistance while you spend time reading something a bit lighter, you can call a local lawn care pro to dethatch your lawn for you. It’ll soon look like a real utopia.
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