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Lawn Dethatching

Over time, different types of lawns accumulate thatch. Bermuda grass is one type that accumulates “thatch” especially if you don’t cut your bermuda grass low.

What is “Thatch”? 

“Thatch” is a layer of fibrous organic material which develops between the green leaves of the grass and the soil surface(usually dead/decomposing grass mixture). In other words, it’s a layer of slowly decomposing grass, dead roots, and other yard debris that’s picked up by your mower and tossed back onto the grass.  A small amount of thatch can be useful to a lawn as it helps to preserve moisture and provide a nice soft feel. Thatch is made up of dead, dying and decaying material from the grass as well as outside sources such as moss and leaves. On a healthy lawn, “thatch” layer can be OK and useful , however through neglect the layer could become too thick, tall or dense.  This cause some issues and problems just like:

• Reduced drainage
• Prevention of moisture and nutrients to the soil and root
• Providing an ideal breeding ground for unfriendly bacteria and fungi that are likely to cause disease
• Increased incidence of Moss and weeds
• Increased incidence of mower scalp
• Unhearly roots for the lawn that cannot get any moisture

A light layer of thatch, up to to one-half inches deep, is actually beneficial to your lawn. It protects the soil from changing temperatures and adds to the resilience of the lawn, which means when you step on it, it springs back instead of compacting the soil. However, even too much of a good thing can be damaging. When your thatch becomes too think it acts as a thatch roof would. It repels water and any other nutrient you try to give your lawn. Thick thatch can prevent water from ever reaching the soil, which results in the grass roots growing in the thatch, instead of the soil. Since the water in the thatch evaporates much quicker than that in the soil, your lawn will become susceptible to drying out quicker than if the roots were planted firmly in the soil.

Some grasses produce more thatch than others. For example, lawns composed of creeping grasses will build up thatch quicker than those that are not. Notorious thatch builders include: Bermuda grass, St. Augustine grass and Zoysia grass. However, dethatching is not recommended for certain type lawns, such as lawns that consist of St. Augustine grass. Also cool-season grasses such as Bentgrass and Kentucky Bluegrass are excessive thatch producers. If your soil is extremely acidic, then any type of grass can build thatch quicker because the microorganisms that decompose the thatch are less active.

Since the thatch keeps the ground temperatures from changing a lot, insects and diseases thrive in thatch-covered lawns. Think about it. It’s warm and moist and cannot be penetrated easily by substances used to control the insects or disease. What better place to live if you’re a grub? Another problem with thatch filled lawns is that the mower will not be able to mow evenly. This will cause other problems such as scalping.

To prevent your thatch from getting too thick, de-thatching is usually performed every other year. You can tell how much thatch has built up by using an aeration device to remove three plugs of soil. The top layer of the plug that looks kind of like peat is your thatch. If it measures more than one-half inch, it is time to de-thatch. It’s best to dethatch your lawn just before it begins growing the most vigorous for the season. For most states, this would be in the spring. If you have cool-season grasses, such as Kentucky Bluegrass, then fall is the best time to dethatch.

How To Dethatch

For many lawns, aeration will be the most useful treatment for moderate thatch. If your thatch is heavier/thicker however, several remedies are available for dethatching.

The most effective way to dethatch is with a machine that is built just for de-thatching called a De-thatcher or vertical mower. These are just like a regular mower, but have a series of revolving blades and cutters that go up and down or spin fast. The blades cut and pull through the thatch to bring it to the surface of the lawn. After you’ve brought the thatch to the surface, you then sweep or rake the lawn to remove the thatch. De-thatchers or vertical mowers can usually be rented from local equipment rental companies.  If you want, you can hire a professional gardener to de-thatch your lawn for a few hundred bucks.

To properly de-thatch your lawn, you must adjust the depth and spacing for the vertical blades for the type of grass in your yard. Bermuda will have shorter lengths while St Augustine may have a longer length.

The cutting knives should completely penetrate the top half of the thatch layer without cutting into the soil at all.  Try an inconspicuous area of your lawn first, before you make some big lines through you grass kingdom.  Always  drive the machine across the lawn in parallel rows to begin, and then de-thatch the entire area again in a crosswise direction also. When you have completed the “De-thatching” process, then always feed your lawn by fertilizing and watering thoroughly so that the moisture penetrates the soil with the beneficial nutrients its been lacking from the thatch.