Is It Time to Dethatch your lawn?

Grass, like other plants, has an underground root system that is topped by a living above ground shoot. Between the root system and the top layer, is a layer known as thatch. Although thatch is natural and beneficial for your lawn, too much of it can create problems in the growth of the grass. Thatch is made up of roots, leaves and stems; some are dead and some are living, so it forms a natural part of the growing process. However, dethatching is essential if the thatch layer is thicker than ½ of an inch. Excess thatch is often caused by lawn care treatments such over watering, over fertilizing with too much nitrogen and/or mowing too high as well as having heavy clay soil.

Problems Caused by Thick Thatch

When there are thick layers of thatch between the root system and the top layer of living grass, it can create a number of problems with the growth by:

  • Blocking sunlight from reaching the lower blades of grass
  • Buildup of moisture which can lead to disease
  • Prevents fertilizer, pest control and/or water from reaching the soil
  • Creates an uneven lawn
  • Leads to shallow rooted grass

How to Know When to Dethatch the Lawn

There are a few things you can do to determine if you need to dethatch the lawn, including:

  • Visually inspect the grass to determine how thick the thatch is. If it is difficult to see the soil, it typically means the thatch is too thick.
  • Feel the grass. A thick layer of thatch will be tough to push your finger through. If the grass feels bouncy or spongy when you stand on it, it usually has a thick layer of thatch.
  • Measure the depth of the thatch by using a hand trowel or a spade to remove a small layer of the grass and soil. If the thatch layer lying on top of the soil is 2 or more inches thick, it’s time to dethatch.

How to Dethatch the Lawn

It is best to use a dethatcher when the lawn is only lightly moist; it shouldn’t be too dry or too wet. The following steps will guide you through the dethatching process:

  • Just before dethatching, mow the grass to about half of its normal height
  • Using a dethatcher, go over the lawn with at least two passes, but change the angles of each pass. For example, do the second pass at a 90-degree angle to the first pass. This will ensure you are removing all of the excess thatch.
  • Use a rake to clean up the debris. The thatch can be used as compost or mulch.
  • If you dethatched about the time when you would apply seasonal fertilizer, apply the fertilizer after dethatching and be sure to thoroughly water the lawn.
  • If dethatching created bare spots reseed and rake the seed into the soil. Cover with organic matter, sand or soil.

After dethatching the lawn, it may look somewhat ragged, but if the dethatching is done at the right time, your lawn will quickly recover, with a healthy fill in. To prevent future thatch, it is important to practice good lawn care techniques, including regular water, fertilizing, mower and aeration.


Contact Ralph Helm Inc. Lawn Equipment Center to learn more information about dethatching, including the best type of lawn care equipment for the task.

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