While most lawn care is simple — mowing, watering, and fertilizing — over time, little bits of grass die and debris gather just above the soil. This is called thatch. A little bit of thatch is great for your yard because thatch is organic material that will be broken down by the soil.
The problem with thatch is that it can build up too fast for the soil to break down, so it will form a barrier that keeps moisture and air from reaching your grass’ roots. A half-inch or more of thatch can weaken your lawn and create problems.
There are two ways you can address your thatch issue — dethatching or aerating.
If your lawn isn’t growing as well as it should, even if you are feeding regularly, your thatch could be too thick or you have compacted soil. Sometimes you have both. Both cases are causing your grass to suffer because water, nutrients, and oxygen are not penetrating through the soil. If your lawn feels spongy and is difficult to stick your finger through to the soil, you have a thatch issue.
What is Dethatching?
Thatch is like an organic mulch that helps conserve soil moisture and helps protect against large fluctuations in soil temperatures. A thin thatch layer will allow water, nutrients, and oxygen to penetrate the soil and reach the roots while acting as an organic mulch that manages soil temperatures.
Ideally, you want to keep your thatch 1/2 an inch or less.
Thatch layers that reach one inch or more will become a barrier instead of a benefit. This amount of thatch restricts your lawn’s ability to absorb nutrients, so your grass suffers. A thick thatch is a breeding ground for lawn disease and pests. This also means the effectiveness of some fungicides and insecticides is reduced.
Dethatching is the process of managing your thatch levels using a dethatching rake or renting a dethatcher. The type of grass, your location, and your mowing consistency play a role in your thatch levels.
When to Dethatch Your Lawn
Over-watering and over-fertilizing your lawn can contribute to a thatch build-up. Infrequent mowing may be great for you, but it’s bad for your lawn. Your goal is to maintain your lawn so that accumulated plant debris decomposes at the same rate as your grass grows.
Mowing height and frequency depends on the type of grass you have. With any grass, use the 1/3 rule when cutting — remove no more than 1/3 of the blade of grass in a single mowing. You may believe grass clippings contribute to a thatch problem, but it does not. Grass is mostly water and decomposes fairly quickly — returning nutrients back to the soil. Mulching mowers speed up this decomposition of smaller clippings.
You should always check your lawn’s thatch layer before dethatching. Take a spade or garden trowel and dig up a small wedge of your lawn — you’ll be able to see and measure your thatch layer. If your lawn is one to two inches, you’ve probably noticed your lawn struggling. Signs of a thick thatch are poor grass color and weak, thin growth.
Dethatch cool-season grasses, like Kentucky bluegrass in late summer or early fall. Warm-season grasses such as Zoysia grass or Bermuda Grass after they green up in the spring as it enters summer’s peak growth. Don’t dethatch your lawn when it is already damaged or stressed — this can damage it beyond recovery.
How to Dethatch Your Lawn
Most lawns you can use a specialized dethatching rake. Rent a dethatcher if you have a larger lawn — you won’t use it enough to justify buying one. Dethatchers are also known as a verticutter, vertical cutter, or a power rake. Most home and garden stores will have one that you can rent.
1.) Before dethatching, cut your grass to half of its normal height.
2.) Use your dethatching rake — it’s similar to using a regular rake. The tines will dig into the thatch and pull it upward to loosen and remove the thatch. While you use the rake, you should feel and see thatch separating from the soil.
If you are going to rent a dethatcher, make any shallow irrigation lines, sprinkler heads, and buried utility lines before starting. Before you leave the store, ask the company to adjust the spacing and cutting depth to your grass type before you leave. The blades should be set so that it cuts no deeper than one-half of an inch into the soil.
3.) Once you are done dethatching the yard, it will look ragged. Grab a rake and rake up the loosened thatch and remove it from your lawn.
4.) If you notice bare spots after dethatching, use a patching product or grass seed to repair them.
What to do After Dethatching
After you dethatch your lawn, overseeding can help get your lawn recover and grow lush and thick. Using a premium grass seed can help improve your lawn’s sustainability as you overcome dethatching. A lawn booster product can combine premium seed, fertilizer, and soil enhancers in one package.
In order to prevent future thatch problems, test your soil every three to four years to keep the soil’s pH and nutrients at optimal levels for healthy grass growth. Use lime to restore your soil’s pH balance and will also promote beneficial thatch-reducing microorganisms.
Fertilize your lawn as recommended and use a low-nitrogen or slow-release fertilizer.
Aerating Your Lawn
Lawns that are heavy or compacted will need to be aerated. Aerating encourages root growth and improves drainage. Aeration annually is recommended for lawns with heavy traffic.
Aeration is the process of making holes in your lawn so your soil loosens. This improves the amount of water, air, and fertilizer that reaches the roots. Aeration also improves drainage and allows grass roots to grow deeper.
You can aerate your lawn with tine or spike aeration, or you could core or plug aerate. Tine aeration uses tines to pierce the soil, but this method could also compact the soil. Core aeration removes plugs of soil from your lawn and helps keep the thatch layer from becoming an issue.