What is Dethatching?

Dethatching may sound like a mind-control scheme straight out of a dystopian thriller, but it’s a little less exciting than that. But what is dethatching, though? 

Dethatching is a process you perform on your lawn to help your grass grow green and healthy. If your lawn starts developing its own spongy, brown carpet, it may be time for a thorough dethatching.

What is lawn dethatching?

Dethatching is an efficient method of removing excess thatch (the layer of debris, dead grass, and other organic matter lying 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 brown 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 lawn pests
• Improve the effectiveness of fertilizer
• Reduce the potential for lawn scalping
• Save water
• Control weeds
• Decrease stormwater runoff
• Reduce puddling and standing water
• Help winterize your lawn and prepare it for spring success

How to tell your lawn needs 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:

1. Use a shovel to remove a small, 3-inch-deep sample of your lawn.
2. Measure the brown, spongy layer between the grass blades and the soil surface.
3. If the brown, spongy layer is over half an inch thick, dethatching is needed to control the thatch in your yard. 

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 lawn
• 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 Zoysiagrass 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, the process of removing plugs of soil from your lawn to decrease compaction.

Unlike dethatching, lawn aeration is proactive and preventative, so you 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. 

Good lawn care and maintenance will determine when to dethatch your yard. With proper yard maintenance and using grass seed that isn’t prone to thatch, homeowners may only need to dethatch their lawn roughly every three to five years or so.

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 a lawn

When choosing a dethatcher, you have four main options: manuel dethatchers, electric detachers, power rakes, or vertical mowers. 

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 your lawn. 

After you’re done dethatching, rake up the debris. For an eco-friendly solution that will help decrease waste piling up in landfills, try backyard composting instead of disposing of the debris.

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: Apply fertilizer and water your lawn after dethatching. It’s also a great idea to overseed your lawn to give it some new green growth.

Pro Tip: If you’re not overseeding, apply a pre-emergent herbicide after dethatching.

Dethatching with a manual dethatcher

Best for: Small lawns with a mild thatch problem (one-half to an inch of thatch buildup).

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.

Dethatching with an electric (corded) dethatcher

Best for: Medium lawns with a mild to medium thatch problem.

Electric 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. 

Dethatching with a power rake

Best for: Larger areas with a serious thatch problem and dense grass that can withstand tougher treatment.

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. 

Dethatching with a vertical mower

Best for: Large lawns with a serious thatch problem that could benefit from overseeding.

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.

• Set the blades to the proper spacing (2 inches or more) and depth (based on your level of thatch). Then, use your verticutter like a lawn mower, making two or more passes across your lawn (perpendicular to each other). 
• It’s a great idea to topdress or overseed your lawn after verticutting.

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.

Reasons why your lawn may have excess thatch: 

1. Overwatering and frequent watering
2. Too much nitrogen fertilizer
3. Poor subsoil quality beneath the sod
4. Absence of earthworms due to pesticide applications
5. Infrequent mowings of tall grass (cutting more than one-third of the grass height)
6. High levels of soil compaction from foot traffic or home construction
7. Nutrient-poor soil with a high clay or sand content
8. Acidic soil with a low level of beneficial microbes

Benefits of having some thatch in your lawn

Thatch isn’t always a lawn menace: A thin layer of thatch (less than half an inch thick) is healthy for your lawn grass. 

Here are the 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 are beneficial organisms that incorporate organic matter from thatch into the soil, increasing soil’s nutrient density.
5. It keeps a steady soil pH, which is the measure of acidity and alkalinity in your yard’s soil. A moderate pH level supplies your turfgrass with the nutrients it needs. 
6. Thatch naturally filters rainwater, straining out contaminants for cleaner groundwater and aquifers.

Problems with thick thatch in your lawn

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.

Thatch thickness

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 and 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. Scalping weakens lawns, causing grass 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, thatch is more manageable in perennial ryegrass or tall fescue lawns. Thatch is more likely to develop in lawns seeded with Kentucky bluegrass, creeping red fescue, and creeping bentgrass.
• For warm-season grasses, managing thatch in Zoysia and bermudgrass lawns is tricky since they 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 in your yard: Some pesticides and fungicides can severely damage the earthworm population.
• Regularly mow your lawn, 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. 

FAQs about dethatching

What chemicals should I avoid to protect my earthworm population? 

Avoid insecticides that include chemicals that are highly toxic to earthworms such as:

• Benomyl
• Captan
• Carbaryl
• Chlorpyrifos
• Fenvalerate
• Guthion
• Methomyl
• Nicotine
• Propoxur

Can I both dethatch and core aerate my lawn?

Absolutely. Dethatching and aerating help your lawn in similar ways, but they provide different benefits. Dethatching rakes up clumps of organic matter that impede the flow of nutrients, while 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.

If I am both dethatching and aerating my lawn, which should I do first? 

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. 

Are grass clippings hurting my lawn and adding to my thatch layer? 

No, the idea that grass clippings cause thatch all by themselves is a myth. Don’t worry about leftover grass clippings on healthy lawns. Grass clippings do wonders for a lawn’s nutrient levels by 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 lawn 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. Dethatching is a worthy DIY project to save your yard, and when combined with the best lawn treatments, 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.

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