Dethatching is a must-do process for your lawn to grow healthier in the future. Every lawn is different, with unique demands. Even if you haven’t dethatched your lawn before, it doesn’t mean you won’t need to do it ever.

If your lawn fails to thrive like it should, the reason may be soil compaction. In such cases, you need to take immediate action.

Therefore, you need to know when to dethatch lawn.

In this blog, we will discuss the best time to dethatch lawn and the correct way to do it.

Learn More: Winter Lawn Care: 12 Essential Tips to Protect Your Grass

What Does Thatch Mean?

A question answer post on what does thatch mean

To know when to dethatch lawn, you must learn what it is and the kinds of grass susceptible to it.

The densely entwined covering of dead and living grass stems, shoots and roots that builds up beneath the greenery and above the earth is called thatch.

Thatch in small amounts is common and even advantageous:

It provides a slight bounce to the turf, which is good for golf balls.

Grass has a thin coating that helps it resist deterioration.

Besides that, it protects grassroots and soil against fluctuations in temperature.

When the organic matter in grass grows faster than it breaks down, lawn thatch forms. 

Although having fast-growing grass seems wonderful, too much thatch buildup compacts the soil and results in a number of issues:

Overly thick thatch can have a variety of causes. The most prevalent ones are overly wet soil (which lowers soil oxygen content), excessive nitrogen (which promotes excessive growth), and inadequately aerated soil. 

The overuse of insecticides, which kills the earthworms and microbes that break down organic debris, is another activity that can cause thatch.

Certain types of lawn grass are more likely than others to grow thatch. 

For instance, Kentucky bluegrass is one the most common grasses in Canada that spreads quickly and accumulates thatch. 

On the other hand, the warm-season grass species Zoysia is less likely to acquire thatch than Bermuda.

Before determining when to dethatch lawn, let’s go through the process of identifying thatch,

You can find out if your lawn has a thatch problem in a few different ways.

Finding out if your grass is brown underneath and green on top is the simplest. 

After you mow, when you’ve just clipped off the top green growth, is the ideal moment to check. 

Thatch causes the lawn to appear dead or brown. You can also test the lawn by walking across it; if it seems spongy, thatch may be the cause.

If you’re still unsure, remove a few tiny plugs from the lawn using a spade or knife. 

The thatch, which is a layer of brown, porous substance that lies between the grass and the earth, can be measured. 

How To Avoid Thatch

An infographic on how to avoid thatch

The best way to reduce thatch development is by prevention. To lessen buildup, choose the right fertilizer number, aerification, mowing, and pesticide application.

With the following methods, you will never stress about when to dethatch lawn.

1. Adding Fertilizer to Your Grass

Fertilization is necessary to keep grass healthy and promote thatch breakdown. 

Fertilize your lawn just enough to keep it growing and looking the way you want it, by choosing the right fertilizer numbers and NPK ratio. 

September is a better time to fertilize in the fall than in the spring since the growth is slower. 

2. Perform Soil Aerification

Thatch builds up more quickly in compacted and poorly-drained soils than in well-drained soils.

Better moisture and air penetration into compacted soils is encouraged by aerification

It also encourages microbial activity that breaks down the thatch layer, resulting in a deeper and healthier root system.

For the aerifier to remain effective over time, it must contain hollow tines or spoons that raise the soil’s cores to the surface.

To speed up the process of the grass filling in the holes created by aeration, fertilize the lawn one week before aerification.

The Best Way to Aerate the Soil

  • For optimal results, run a core aerifier over the grass multiple times in various directions to loosen up compacted soil.
  • Before raking the soil cores back into the lawn, let them partially dry.
  • Additionally, cores can be left on the surface to disintegrate gradually. Use soil that has the right microbes to break down thatch.
  • Depending on how far north you live, late August to early October is the ideal period to aerate.

Aerification in the spring or summer can also be effective, particularly if it is accompanied by frequent and regular watering. 

Aerify the lawn only after you’ve mowed it twice in the spring. After aerifying the grass, apply a pre-emergence pesticide to assist in stopping the emergence of annual weeds unless you plan to reseed it.

By following this practice, when to dethatch lawn will be the least of concern.

3. Cutting Grass

You don’t need to bag the grass clippings if you mow your lawn frequently enough to remove no more than one-third of the leaf height with each mowing. 

Tiny grass clippings quickly break down and return nutrients to the lawn by filtering down into the grass. 

Nonetheless, the clippings must be evenly dispersed rather than piled if you don’t ever want to deal with questions like the best time to dethatch lawn.

Although you can let grass clippings return to the lawn without using a mulching mower, mulching mowers do so much more evenly than conventional mowers. 

However, the amount of time between lawn mows does not increase while using a mulching mower. The grass’s growth rate determines how often it has to be mowed.

4. Apply Insecticides

If you want to avoid wasting time figuring out when to dethatch lawn, refrain from applying chemical pesticides. 

Numerous pesticides have an impact on the populations of earthworms and microorganisms that break down the thatch layer.

Pesticides should only be used once a pest issue has been properly diagnosed.

You can use the organic methods of pest control as well to prevent your lawn from damage.

When to Dethatch Lawn

An answer to when to dethatch lawn in Ontario

It’s time to dethatch if your thatch is more than 12 millimetres thick.

Similar to other significant lawn tasks, like sod installation or overseeding, dethatching has to take place within the prime growing seasons of your particular grass variety. 

Active grass growth facilitates a quicker recovery for your lawn.

Never dethatch a stressed or dormant grass, as you risk irreversible damage.

Dethatching aids in slicing through the thick, collected organic debris layer to expose the soil beneath the thatch.

Here are the steps to know when to dethatch lawn:

Examine and touch your grass. Your grass probably has a heavy covering of thatch if it feels bouncy when you walk on it.

Examine your yard from below. Is the dirt visible through the grass’s leaves? Can you see a coating of thatch with your finger? It has to be dethatched if your finger cannot pass through.

The thatch can be measured with a ruler. 

To remove a wedge-shaped layer of your grass and soil approximately 7.5 centimetres thick, gently use a tiny spade or your fingers to dig up a small patch of turf. 

On top of the soil, look for a layer of thatch and determine the thickness. 

Additionally, don’t dethatch a newly planted lawn before it has had a full summer. That is because to withstand the heat, the lawn needs to establish a robust root system. 

How to Dethatch Lawn By Yourself 

Removing excessive thatch may require multiple sessions, as removing too much at once may cause damage to the grassroots.

You can get assistance choosing a route from your local county extension agent. After knowing when to dethatch lawn, use these methods to do it.

The hefty, short-tined rakes used for manual dethatching have curved blades that dig into your lawn and lift thatch as you rake.

For mild thatch and general thatch management on small lawn areas, dethatching rakes work well.

Mower-like tools with rotating rake-like tines that remove thatch at the soil’s surface are called power rakes.

Lawns with grass that can tolerate vigorous raking and thinner thatch levels are ideal candidates for power rakes.

Verticutters, another name for vertical mowers, are equipped with vertical blades that cut through the layer of thatch and into the soil, bringing thatch and frequently grassroots to the surface as they go. 

The best tools for thick thatch layers on lawns that require repair are verticutters. Blades adjust to regulate the amount of thatch removed in one stroke.

Hiring a Professional to Dethatch a Lawn 

Although dethatching a lawn is not a difficult task, it can take a lot of time and physical labour.

Particularly if the lawn is vast, the thatch layer is thick, and dethatching has not been done in a long time.

Also, if you make a mistake in determining when to dethatch lawn, it may lead to irreversible damage to it.

Hence, it may be more cost-effective to employ a lawn care professional to complete this task, given their equipment and speed.

With their expertise, they can decide the best time to dethatch lawn. Above all, they can take care of other seasonal lawn care tasks like core aeration as well. 

Professionals with experience with power dethatchers are less likely to cause damage to the lawn than a homeowner making their first rental tool use.

To make dethatching a lot simpler, take care of the lawn during spring by raking, watering, and performing other important tasks.

Cool-Season Grass That May Need Dethatching 

A list infographic of cool season grass

If you are searching for when to dethatch lawn because you are planning to grow new grass, these are the types of grass popular in Ontario.

1. Kentucky Bluegrass 

Kentucky bluegrass yields a bluish-green lawn that is dense and hardy. It can withstand extreme cold well but not as well as drought. 

2. Tall Fescue

A great drought-tolerant substitute for Kentucky bluegrass is tall fescue. It requires frequent mowing due to its rapid growth. 

3. Fine Fescues

Fine fescues can withstand a lot of shade but not a lot of foot traffic. Crinkling red fescue, hard fescue, sheep fescue, and chewings fescue are some of the species. 

4. Ryegrass 

Fast-growing perennial ryegrass can withstand a lot of foot traffic. For warm-season lawns, it can be grown as a temporary wintergreen or as a permanent grass. 

Things to Keep in Mind After Dethatching

Although thatch will always exist, proper lawn care techniques can lessen its intensity over time. 

For normal growth, apply the appropriate kind and quantity of fertilizer. You should retain the appropriate pH levels by making adjustments. And to provide space for new growth, aerate your lawn frequently.


How would I know when to dethatch lawn?

Always inspect the layer of thatch on your grass. Dig up a tiny wedge of your lawn’s grass and dirt with a garden trowel or spade. Thatch layer will be visible to you and measurable. 

What symptoms help in determining when to dethatch lawn?

You may notice symptoms of weak, thin growth and poor grass colour if there is detrimental thatch in your lawn. 

When is the best time to dethatch lawn?

Late spring or early summer is the ideal time to dethatch. To give your lawn the best opportunity of recovering to health, avoid dethatching during the hottest time of the summer.

In Conclusion

This was our account on when to dethatch lawn.

If the thatch is deeper than ½ inch in lawns, dethatching is necessary. Although dethatching and lawn aeration are two distinct procedures, they can complement one another to improve your lawn. 

By removing soil cores and their thatch layer, aeration makes it possible for water and nutrients to pass through compacted soil and thatch. 

This facilitates the decomposition of existing thatch more quickly and helps prepare thatch for removal.