Lawn Dethatching: Everything You Need to Know

Excessive thatch can completely destroy your lawn. Luckily, dethatching can prevent problems and save your lawn.

What Is Thatch?

Thatch is a mixture of dead and living grass, stems, and roots that form a layer on the top portion of your lawns root system.

What Causes Thatch?

Thatch is caused when your lawns soil can’t breakdown organic matter at the same rate it’s entering your soil.

You have to remember, even a healthy lawn has grass blades that die back as new ones form.

On top of that, you cut your lawn and that means the top portion of the grass blades enter back into your lawn, especially if you mulch your clippings.

This is natural, and healthy for your lawn as long as the clippings and spent grass enters your soil at a rate slow enough for your soil to break it down.

To keep that healthy balance, avoid the following:

1. Synthetic fertilizers. Synthetic fertilizers give you a quick blast of nitrogen which causes your lawn to grow rapidly. This artificially accelerates the growth cycle of your lawn which means grass blades die off quicker to make way for new growth.

It also means more frequent mowing which puts a stress on your lawns soil since it has to break down those clippings. Even if you bag your clippings a good percentage of clippings are still left behind.

2. Poor aeration and drainage. Soil needs air to break up thatch. Poor aeration and drainage prevents air from entering your lawns soil.

3. Too much watering. Watering too frequently will cause a shallow root system. You want grass roots to grow deep into the soil. A shallow root system means a weaker lawn which can’t hold up to drought, fungus, or other problems.

4. Too little watering. If your lawn is too dry you’re going to get a lot of grass dying back when the heat of the summer kicks in. This high rate of dying grass will out compete your soils ability to break it down.

Why Is Thatch Bad?

A thick layer of thatch will suffocate your lawns root system and deprive it of water and nutrients. Any attempt to fertilize or water your lawn will be ineffective since the thatch layer acts as a barrier.

How to Know If You Have a Thatch Problem?

A little bit of thatch is normal, even healthy up to about a 1/2” thick. But anything over a 1/2” is bad for your lawn.

You can tell your thatch layer is too thick if your lawn feels spongy or bouncy, or like you’re walking on a thin cushion. Also, for visual queues look to see if your lawn is looking thin, or not responding to fertilizer treatments.

If you suspect you have a thatch problem, cut out a section of your lawn about 6” wide x 6” long, and 6” deep. Take a look at the thatch layer too see if it’s more then half an inch.

How to Remove Thatch?

Once you’ve confirmed you have a thatch problem, it’s time to fix it using one or more of these methods:

1. Manual removal with dethatching rake. This is a special rake that is specifically designed to dig into the thatch layer of your lawn and pull it out. These rakes are effective but can add up to a lot of manual labor. They are best suited for smaller lawns and lawns with a small to medium thatch problem.

2. Use a tine rake dethatcher. A tine rake dethatcher is usually mounted to a ride on mower or tractor, but they also have a hand held version that works for smaller lawns.

Tine rake dethatchers work by using thin metal tines that scrape the surface of your lawn. This loosens up any dead grass or leaves and can then be sucked up while mowing.

Tine rake dethatchers are great spring cleanup tools, especially the ones that get mounted to your mower or tractor. They don’t require a lot of labor and it doesn’t take much more time then if you were to just mow your lawn.

Since tine rake dethatchers don’t really get into the true thatch zone of your lawn, they are better suited as a way of preventing thatch buildup or reducing the amount near the surface of your lawn.

3. Core aeration. Core aeration is made possible by the use of a machine called a core aerator. A core aerator has hollow metal tines that penetrate into your lawns soil. These hollow tines pull out plugs, or cores of your lawn, creating tons of small holes throughout.

Since the metal tines go deep into the soil, they break up that thatch layer and pull it out.

Also, the increased air flow into the soil allows microbes to break down thatch. Core aeration is great for preventing thatch problems and fixing small to medium existing thatch problems.

4. Power raking. If you have a serious thatch problem, the only real way to deal with it is to use a machine called a power rake.

It can be confusing because sometimes these machines are referred to as dethatchers. When trying to rent or purchase one of these machines just make sure it is suited to do the job you want it to do. In this case you want a machine that cuts slices into your soil and pulls out thatch.

These machines are usually walk behind and can be a bit labor intensive. It can be shocking to see how much thatch comes up when using one of these machines.

When to Dethatch Lawn?

Dethatching should be done when your lawn is actively growing and not under any environmental stresses such as drought.

For cool season grasses, early fall is best. Avoid dethatching with power rakes in early spring since the ground is too wet and the grass is still dormant. This will cause too much damage.

For warm season grasses, late spring/early summer is the best time to dethatch.

How to Prevent Thatch Buildup?

1. Use organic fertilizers. Organic fertilizers are slow release and don’t cause rapid growth of vegetation which can cause thatch problems.

2. Cut your lawn frequently, and bag your clippings. This will decrease the amount of organic matter your lawns soil has to break down.

3. Core Aerate. Core aeration has many benefits and is great to add to your lawn care program. If you can’t do it every year then every other year is still a big help.

4. Irrigate deeply, and less frequently. If you have an irrigation system then set a watering schedule that focuses on less watering days, but for a longer watering duration. Deep watering causes roots to grow deep. Frequent, shallow watering causes a shallow root system and is more likely to cause thatch problems.

How Often Should You Dethatch Your Lawn?

Dethatching using a power rake should only be done if your thatch layer is greater then 1/2”. Otherwise, stick to the preventative measures to avoid problems.

What to Do After Dethatching?

After dethatching, rake up the newly exposed thatch. Mowing your lawn will also help to clean things up. Fertilizing at this time is also important. This will help your lawn recover and fill in any bare spots.