There are many things dealing with the lawn and garden that are very beneficial in small amounts, but quickly turn detrimental in large quantities. Fertilizer, irrigation and pruning are some good examples of this. The trick is finding the proper balance in everything we do. Another great example of this concept is the thatch layer in lawns, the topic of this week’s blog post. Many homeowners are unsure or unfamiliar with thatch, what impact it has on lawns, when to dethatch and how to go about removing it.

What is Thatch?

The thatch layer is the area between the green grass blades and the soil surface. It contains dead and living organic matter such as stems, stolons, rhizomes and roots. A thatch layer is important to a strong, vigorous lawn and can help reduce weed germination and increase moisture retention in the soil. However, too much thatch or not enough thatch can be a problem. Too much thatch can act as a barrier between the grass and soil which prevents air, water and nutrients from penetrating the soil surface and reduces root growth. This can stress the grass and will weaken its ability to fight pests, diseases and drought. On the other hand the absence of a thatch layer will cause the soil to dry out faster, making the lawn more susceptible to drought stress. Thatch also adds beneficial nutrients and organic matter to the soil as it decomposes. 

Excessive Thatch

A thatch layer is considered excessive when it’s more than ½ inch thick. To find out if your grass is suffering from excessive thatch, simply dig up a small section of your lawn with a shovel or hand trowel and examine it from the side. Measure the brown layer between the soil surface and the green grass blades. If it’s thicker than ½ inch, it’s time to consider dethatching your lawn. 

Why a Lawn May Be Developing Excessive Thatch

There are many reasons why thatch might be building up. A lot of it has to do with the species of grass used in your lawn. Grasses such as perennial ryegrass and fescue tend to produce the least amount of thatch while grasses like Bermudagrass and zoysia grass produce the most thanks to their aggressive, creeping growth habits. Buffalograss and Kentucky bluegrass are considered moderate thatch producers. Excessive thatch also tends to build up in lawns that are over-fertilized, over-watered and not mowed regularly. Mulching or leaving grass clippings on a regularly mowed lawn does not contribute to the thatch layer since they break down rapidly. In fact, this practice is a good way to add nutrients back into the soil and reduces the amount of fertilizer a lawn needs. 

Dethatching Methods

If you’ve determined that it’s time to dethatch your lawn, you have a few options. First, mow your lawn slightly lower than normal to help access the thatch layer. The simplest method is to use a thatching rake. Thatching rakes are best used on small lawns since they’re also the most labor intensive method of dethatching. These specially designed human-powered rakes use thin blades that loosen and pull the thatch to the surface where it’s gathered and discarded. For medium to large lawns, mechanical power rakes or vertical mowers are better suited. With revolving blades that cut vertically into the thatch layer, these machines are able to remove a large amount of thatch without much effort. Most professional lawn care services will dethatch a lawn, or you can do it yourself by renting a vertical mower or power rake from an equipment rental center. 

When to Dethatch

Because dethatching can be stressful for a lawn, it’s important to time it right. Only dethatch during an active growing time. For cool-season lawns this is during the spring or fall. Dethatch warm-season grasses only in the summer. Remember to never use heavy equipment on a wet lawn. After dethatching it’s a good idea to fertilize and irrigate the lawn to encourage recovery. Overseeding may also be necessary.