When to Dethatch Lawns and Dethatching Tips

Have you noticed a buildup of excessive roots, stems and organic matter in your lawn? That’s thatch — a cross-section of soil, and grass roots that may be invisible to the naked eye, especially if you’re looking at your lawn from a standing height.

In fact, many lawn owners have no idea when to dethatch lawns, or even what thatch is and how it may affect the overall health of their grass. Removing this tightly interwoven layer of living and dead plant matter is not a necessity, but is highly recommended if you want to rejuvenate your lawn and let your grass breathe.

What is Dethatching?

Dethatching is the process of removing this layer of mostly dead stems, leaves and grass roots to replenish the soil with air, water, fertilizer, and essential nutrients. Allowing thatch to accumulate reduces your lawns tolerance to drought, cold and heat stress, and increases your turf’s susceptibility to lawn diseases.

Thatch buildup in the worst cases restricts the grass roots from growing into the underlying soil, meaning they only take root in the layer of thatch.

However, dethatching or physical removal of thatch will not necessarily benefit all thatch plagued lawns, sometimes your lawn may just be lacking the beneficial microbes it needs to naturally dethatch or prevent thatching.

knowing when to dethatch lawns is useful
Person cutting grass with mower

What Causes Thatch Buildup in Lawns?

Thatch buildup is a good sign that your lawn is lacking beneficial microbial activity. It will continue to accumulate if your lawn’s ability to produce dead material (organic matter) surpasses the ability of the microorganisms to break down the dead material.  

There are myriad different reasons for thatch buildup in lawns, most notably:

  • Poor soil aeration and drainage
  • Bad lawn watering practices
  • Using chemical pesticides
  • Cold soil temperatures
  • Not mowing the lawn frequently

How Do You Know if Your Lawn Needs Dethatching?

Dethatching can be a daunting task, which is why it’s highly important that you assess your lawn to determine if you’ve got a thatch problem, to begin with. A thatch layer that’s thicker than 1/2- to 3/4-inches is considered excessive, which means you’ll have to dethatch physically.

You can even see the thatch layer by combing your fingers through the grass, and checking to see if you can see any soil between the grass blades. If you don’t see any soil between the grass blades, then it’s time to prepare to dethatch.

Another way to check if you have a thatch issue is to poke your fingers between the blades of grass to see if it feels springy or spongy. If it does, then you can cut a vertical slice from the turf, and measure the thickness of the thatch layer with a ruler.

When to Dethatch Lawns?

Getting back to the main question — when should you dethatch your lawn? Well, lawn experts recommend dethatching grass during the period of active growth, and the warm temperatures of spring.

However, the exact time to dethatch grass in spring depends on the type of turf you have. Further, for the best results you should dethatch your grass after mowing it a couple times to about half its normal height.

Warm-season grasses such as Bermudagrass or Zoysia grass should be dethatched in late spring to early summer, whereas cool-season grasses such as Kentucky Bluegrass, Fescue and Ryegrass are best dethatched in the late summer or early fall.

 

Should You Dethatch the Entire Lawn?

Many homeowners ask if it’s a good idea to dethatch the entire lawn in one go, and the short answer is absolutely not! In fact, by doing this, you risk removing all the thatch and soil from one area, and not removing enough from other areas.

This is why it’s highly important that you carefully inspect each area of your lawn, and take note of areas with excess thatch.

Dethatching vs Aerating Lawn

Aerating as opposed to dethatching may seem a preferable option on paper, but they’re two completely different lawn care processes. Both procedures are geared towards enhancing the breathability of the soil and the ability of the grass to soak up the essential nutrients, but the two processes help your lawn in different ways.

Dethatching, as the name suggests, is the process of removing thatch (leaves, grass clippings, flowers) from the soil surface. Thatch however does offer certain key benefits for your soil such as keeping it moist by acting as a mulch, providing a constant infusion of nutrients, as well as insulating the soil from extreme temperatures.

Thatch only becomes a problem when the layer is too thick, causing the grass roots to suffocate, thereby killing the grass. Thatch that is too thick should be dethatched leaving only a healthy layer on the soil surface.

Lawn aeration is similar to dethatching in that it helps the soil under your lawn to breathe, but it is a procedure that helps ‘control’ thatch rather than actually get rid of an excessive build up.

There are a range of manual lawn aerators available to help you with small scale lawn aeration. If you have a large grass area to aerate, then you will likely need a more substantial machine

To explain briefly; aerating involves making holes (through any existing thatch layer) in your lawn to allow essential nutrients (oxygen, fertilizer and water) to easily reach the grass root layer, whereas dethatching removes the layer of dead material that accumulates on top of the soil, thereby allowing the nutrients easier access to the roots of the grass.

Tools for Dethatching a Lawn

It goes without saying that to dethatch your lawn properly, you need tools designed for the job.

How to Use a Dethatching Rake to Remove Thatch?

Often referred to as a thatching rake, a dethatching rake is not the same as a leaf/lawn rake. A dethatching rake is quite substantial and features sharp teeth on both sides of its head that can dig in between the grass blades, whereas the leaf/lawn rake has tines that fan out in a triangle on one side and is lightweight so that it can be passed over the surface of the grass to gather leaves or grass cuttings without digging into the turf and disturbing the roots.

A dethatching rake is used by pulling it through the grass towards you to pull up the thatch, then pushing it away from you to remove the thatch from the blades, ready for the next pull.

How to Use a Dethatcher to Remove Thatch?

A lawn dethatcher is a small machine that’s fitted with spring tines, which rotate and dislodge the layer of thatch. Dethatchers are a great choice for less than half an inch of thatch, and are easy to use. You just start up the machine, set the blade height and then simply pass it over the areas of grass that need dethatching.

How to Use a Power Rake to Remove Thatch?

If you have thatch that’s over half an inch, then a power rake is the tool you need. This tool can remove up to four times the amount of thatch compared to a dethatcher, but should be used early, as it can be very unforgiving on your lawn.

A power rake loosens the thatch using spinning flails that spin at a very high speed. The thatch that is loosened is then picked up by the power rake, leaving your soil much more exposed than before. Before you power rake your lawn, it’s a good idea to run a test pass on a small area, and then another test pass in a different direction.

How Often Should You Dethatch Your Lawn?

The number of times to dethatch your lawn for the most part depends on the type of grass you have, and the growing conditions. Some types of grass such as Bermuda grass and Zoysia grass tend to produce more thatch, whereas Bluegrass and Ryegrass a moderate amount of thatch, and Tall Fescue produces the least thatch.

However, it’s worth noting that regardless of the type of grass. Your lawn will need dethatching at least once a year, or when the thickness of the thatch reaches about half an inch. Dethatching is unwarranted if the layer of thatch is less than half an inch, and doing so at this height will possibly damage healthy grass.

How to Get Rid of Thatch Naturally?

There are a few things you can do to remove thatch without using any tools such as consistently keeping the soil moist under the layer of thatch. Keeping the soil moist below the layer of thatch increases the speed of decomposition of the thatch layer.

Adding to this, it’s a good practice to collect your grass clippings regularly until you get rid of the thatch layer. Keep tabs on your soil’s acidic level and ensuring that it isn’t too acidic could slow down thatch build up over time.

Final Thoughts

If you have thatch that’s over 1.5 inches deep, then you may want to consider digging up your lawn, and starting over with a grass that doesn’t produce a lot of thatch.

It is important that you refrain from fertilizing your lawn before dethatching, but do it after to help your lawn recover.

As the saying goes “prevention is better than cure”, improving your soil, so that it’s aerated and bioactive enough to allow the thatch to decompose is a great way of removing thatch naturally from grass.

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