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What is Dethatching and How to Dethatch Your Lawn

If the height of thatch measures more than 1.5 cm, then it’s time to dethatch your lawn.

If your lawn is looking less than perfect or if you notice some discoloured, dry patches after you mow, you might have a build-up of thatch and it might be time to dethatch your lawn.

What is lawn thatch?

Lawn thatch is a build-up of organic material such as dead grass and grass stolon and rhizomes that have not broken down.

This creates an almost impenetrable thick layer under your grass and stops the water from penetrating into the soil below.

It can often result from irregular mowing and is more common in vigorously growing grasses. 

Bear in mind though, that a thin layer of thatch under your grass is often good for your lawn as it can act as a mulch to help keep the moisture in the soil longer and protect the roots from extreme heat. A thatch layer of around 1.5 cm is usually considered beneficial.

What are the benefits of dethatching your lawn?

Dethatching breaks up the impenetrable layer that has formed under the grass and helps to open up the soil. This makes it easier for both water and fertiliser to reach the growing roots of your grass.

While a thin layer of thatch is beneficial, too much thatch can cause shallow root growth in your grass. This makes the lawn less drought-tolerant than it should be. 

Too much thatch can also cause root rot or other types of diseases in your lawn. Therefore, dethatching helps to keep your lawn much healthier and more drought-tolerant.

How do I know if my lawn needs dethatching?

You’ll know that your lawn needs dethatching if you notice dry patches with uneven growth after you’ve mowed your lawn. To test the layer of thatch, you can dig up a small piece of lawn where you see a dry or discoloured patch and measure the layer of thatch in the section.

If the height of dead material or thatch in the piece of lawn you’ve dug up measures more than 1.5 cm, then it’s time to dethatch your lawn.

Another way to determine whether your lawn needs dethatching is to walk over it and look for uneven patches that look somewhat dry. If there is a build-up of thatch, these areas will feel quite spongy underfoot.

Do all types of grass need dethatching?

Dethatching is generally only recommended for warm-season grasses such as Kikuyu, Couch, Buffalo, and Zoysia. 

For cool-season grasses that primarily grow over winter, it’s better to use coring. This involves opening up small sections of soil to then topdress the lawn.

If you really do have a problem with thatch in your cool-season lawn, you can try using a power rake in autumn.

How to dethatch your lawn

There are several ways that you can dethatch your lawn to bring it back to its former glory.

Scalping using your lawn mower

Lawn mower 1 | Lawn care

Scalping is a method that works quite well with Kikuyu and Couch. It’s the process of cutting your lawn at the lowest possible setting on your mower.

Essentially, you’re removing as much of the top layer as possible in order to open up the lawn so that water and fertiliser can penetrate into the soil.

Using a dethatching rake

Thatching Rake 1 | Lawn care

Dethatching rakes are available from most hardware stores and garden centres around Australia. With a dethatching rake, you’re manually breaking up the dead layer under the grass to open up the soil.

This is quite labour-intensive but is considered the least disruptive method to dethatch your lawn.

Therefore, if you only have a small lawn, you might like to consider this method over using more mechanical ways to dethatch your lawn.

After working the lawn with the rake, it’s also important to remove all the dead layers that you’ve uncovered from the top of your lawn.

Using a power rake

Bulldog Lawn yard dethatcher Power Rake Honda GX160 | Lawn care
Bulldog Power Rake (view at eBay)

A power rake is a mechanised machine that works similarly to a dethatching rake but with less effort on your behalf. As these machines can be quite expensive, a better idea is to hire one. This can be relatively cost-effective because you’re only going to need it once a year at most.

A power rake should be used on damp but not saturated soil. It’s a good idea to water your lawn the day before you intend to dethatch it. Make sure that you set the height of the tines so that they break up the thatch without digging out the soil.

Using a lawn scarifier

Greenworks 40V Dethatcher | Lawn care
Greenworks Dethatcher and Scarifier (View at Amazon)

A lawn scarifier works in the same manner as a dethatching rake to break up the dead layer under the grass and bring it to the surface.

However, a lawn scarifier is often only used when you have a very heavy layer of thatch because it will dig into the soil as well.

What time of year is best to dethatch lawns in Australia?

If your lawn is made up of warm-season grasses that grow primarily during the warmer months such as Kikuyu, Couch, Zoysia, and Buffalo, it’s best to dethatch your lawn in late October through to early December.

This is because warm-season grasses have not fully recovered from their winter dormancy until mid-spring. 

If you dethatch your lawn in early spring, it will take longer to recover and will look quite bare for a month or so. This also allows weeds to grow more abundantly which can cause you even more problems.

It’s also recommended that you don’t dethatch a new lawn until it has had at least one full growing season over summer and to avoid dethatching any lawn after January.

At this time of the year, many lawns are under a bit of stress from hot and dry weather and will recover much slower.

How to maintain your lawn after dethatching

Once you’ve dethatched your lawn and removed all the dead material that has been brought to the surface, it’s important to apply some fertiliser and water it well.

This will help the lawn to recover much faster and it will start to look better within a few weeks.

Dethatching vs Aerating: What’s the difference?

While dethatching removes the thick layer of dead material under the actively growing grass, aerating is the process of removing plugs of soil in order to let more moisture and nutrients in. It also increases the oxygen in the soil and improves microbial activity.

In general, dethatching should be done before aerating the soil if the lawn is quite spongy and has dry and uneven patches.

However, aerating is particularly useful in compacted soils to help loosen them up and promote better grass growth.

FAQ

Is dethatching really necessary?

If the thatch layer is less than 1.5 cm in depth, then dethatching is not necessary.

Do I need to mow before dethatching?

It’s recommended that you mow your lawn to half its normal height before dethatching.

How do you stop thatch buildup?

The best way to stop thatch build-up is to mow your lawn regularly and to mow low during the main growing season over late spring and summer.

What happens if you dethatch too early?

If you dethatch your lawn too early in spring, it will take much longer for it to recover.

Photo of author

Annette Hird

Annette Hird is a gardening expert with many years of experience in a range of gardening related positions. She has an Associate Diploma of Applied Science in Horticulture and has worked in a variety of production nurseries, primarily as a propagator. She has also been responsible for a large homestead garden that included lawn care, fruit trees, roses and many other ornamental plants. More recently, Annette has concentrated on improving the garden landscape of the homes that she has lived in and focused a lot of energy on growing edible plants as well. She now enjoys sharing her experience and knowledge with others by writing articles about all facets of gardening and growing plants.

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