Dethatch or Scarify Your Lawn: A Guide for Homeowners

Dethatching and scarifying are lawn care practices that involve removing dead grass, moss and organic matter from the surface of your lawn to encourage healthy grass growth. This process is a necessary task for creating and maintaining a healthy green lawn.

What is thatch?

Thatch is a layer of dead and almost dead grass material that accumulates under the surface of your lawn. Thatch is a natural occurrence but when the dead material decomposes too slowly, the layer thickens and becomes problematic for healthy growth.

When the thatch layer becomes too thick it can prevent water, nutrients, sunlight and oxygen from reaching the roots of your grass. This leads to an unhealthy lawn susceptible to fungal disease, and prevents new healthy grass growth. Other effects can be uneven growth and particularly spongey patches.

Do you have moss in your lawn?

If you have moss in your lawn we would recommend treating the moss before you try to remove it otherwise you run the risk of simply spreading the problem. Follow the instructions on your lawn treatment and allow the moss to die before removal.

In the remainder of this article, when we talk about the removal of thatch this includes both thatch and moss.

The difference between dethatching and scarifying

Dethatching and scarifying are both lawn care practices that involve removing debris, moss and organic matter from the base of your grass. While both processes can help improve the health of your lawn, dethatching is used to remove a thinner layer of thatch, while scarifying is more aggressive and cuts deeper into the lawn to remove thicker layers of thatch.

Dethatcher/scarifier with metal blades and spring tines

What is dethatching?

The dethatching process normally involves metal tines raking across the surface of the lawn to pull up the thatch, without causing too much of a visual impact to the turf. Once the thatch has been pulled up it should be collected for recycling.

What is scarifying?

The scarifying process normally involves metal blades cutting deep into the lawn to pull up thick layers of thatch. The process is more aggressive than dethatching and your lawn will require time to recover afterwards. Be warned! A scarified lawn will look like it has been ruined. But don't worry. That is normal.

A lawn that has been scarified

When to dethatch or scarify your lawn

The most suitable time to dethatch or scarify your lawn is in the autumn as the temperatures are cooling but the grass is still growing and there is a high probability of rain.

You can also scarify in early spring before the main growing season, but you need to be reasonably certain of warm weather and rain to allow the grass to recover.

Dethatching and scarifying at these times will help the lawn to recover quicker.

You should avoid dethatching and scarifying during the winter when the grass is dormant and at the peak of summer when temperatures are high as this may stunt and delay recovery.

How to dethatch or scarify your lawn

Before dethatching or scarifying we'd recommend mowing your lawn to a low height. This will make it easier to both see the thatch and provide better access to the layer of thatch for removal.

There are two main ways to dethatch or scarify your lawn: manually with a dethatching rake or with a powered dethatcher/scarifier.

To manually dethatch a lawn you will need a dethatching rake, also known as a spring tine rake. These rakes have sharp tines that cut through the thatch layer and pull it upwards from the base of the lawn.

Spring Tine Rake

This can be physical work and won't be a quick job, so is only recommended for small lawns or light dethatching. To use a dethatching rake, simply rake the surface of the lawn, then overlap your rakes in the opposite direction to ensure all the dead grass is removed.

For larger lawns and lawns with a lot of thick thatch we would recommend using a powered dethatcher or scarifier. These machines can look similar to a lawn mower, but instead of cutting blades there are a series of tines or metal blades that cut through the thatch and remove it from the base of the lawn. Before using any powered equipment be sure to read the operator manual and take note of all safety precautions.

If your dethatcher or scarifier doesn't collect the thatch into a catcher or box, you will need to remove thatch and debris from the surface of your lawn yourself. This can be done by raking or by using your rotary mower. Set your mower to a high cutting height then run the mower over your lawn. This should do a good job in collecting your thatch.

We'd also recommend watering and fertilising your lawn after dethatching as this will aid recovery and encourage new growth.

How to tell that your lawn needs dethatching or scarifying

There are a few signs that a lawn may need dethatching or scarifying. Here are some things you should look out for:

• If your grass is thinning or not growing as well as it used to, this could be a sign that a layer of thatch has grown and is preventing water, nutrients and oxygen from reaching the grass roots.
• If your lawn feels spongy when you walk on it, this could be a sign the thatch layer is too thick.

• If your lawn has visible matted patches, it's often a sign that beneath there is a thick layer of thatch.

How often you should dethatch or scarify your lawn

This depends entirely on multiple factors, so you are best to look at your lawn and make an educated decision. As a good rule of thumb, dethatching is a little and often task whereas scarifying tends to be a once or twice a year job.

If you're aiming to maintain a fine lawn, then dethatching and scarifying are likely to be part of your wider lawn care plan.