When to Dethatch and Aerate Your Lawn

By Donna Dolinar, Wyandotte County Extension Master Gardener since 2006

Homeowners are often confused about landscaping maintenance. Many of the terms and procedures seem the same or similar and it can be bewildering. Here are a couple of items that you should understand: dethatching and aerating.

Thatch

First, you need to know what thatch is. Thatch is a layer that forms from the grass clippings and other organic matter that will mix with the shoots, stems and roots of turf. It simply accumulates over time and can be accelerated from compaction. A layer of about a half inch is good because it crowds out weeds, helps keep the soil at an even temperature, and protects the top of the soil.

Too much thatch and you are harming the lawn because air cannot move to the plant roots as easily. It also creates a layer that will prevent water and fertilizers from penetrating the soil to get to the root system. The lawn suffers and becomes more susceptible to inclement weather conditions and insects.

Excessive thatch can be prevented by proper watering. That means avoiding frequent or shallow irrigation on established landscapes. Don’t over fertilize. Proper mowing is another factor. Don’t remove any more than one-third of the blade at the time of mowing. There are other valid reasons for this height, but that is another story.

Dethatching

Dethatching is a process that removes some of that excess material and is handled by a machine cleverly called a dethatcher. These are machines that can be rented at stores that specialize in large mechanical items. You can also hire it done by a reputable lawn service.

If you have a riding mower or lawn tractor, you can also use an attachment. This is usually a pull-behind contraption that has tines to pull up the material. Before beginning, mow the yard to the shortest acceptable length for the type of turf and geographic conditions. If you have an irrigation system, mark all of the sprinkler heads with flags. Don’t rely on your memory or you will need to have any damaged heads replaced.

If you are using this method, give the entire lawn at least two passes. This will give you the best chance to take off enough to make the effort worth it. You may need to periodically stop and clear the tines of thatch that has accumulated on them. Use all safety precautions.

After the dethatching is complete, you need to remove all of the organic matter you dredged up. If you only have a small space, you can use a rake. For medium to large lawns, you can either mow again and use the bagger attachment, or you can use a vacuum on your riding mower. You may be surprised at the amount you accumulate. This debris is significantly heavier than you may suspect. Put all the debris on your compost pile or use it for mulch in your flower beds.

Aeration

Aeration is poking holes in your lawn so that air and nutrients can reach the root system. This is another machine or attachment to your riding mower.

There are two basic types of aerators. The first one has spikes that look like arrowheads and this will push a hole into the ground. This is the less preferred method because the spikes actually compress the soil around the hole, which is exactly the opposite of what you are trying to accomplish.

A better option is a core aerator. This extracts a plug of soil and drops it back into the yard. Don’t worry about those plugs. They will eventually disintegrate and return to the ground. Once the ground is aerated, you can overseed or fertilize as necessary.

Dethatching, thatch removal, and aeration can all be handled in the same day but should be done in exactly that order.

Few homeowners can afford or want to invest in all that equipment. That is when it is nice to know your neighbors and co-op the process. Three riding mowers can finish half a dozen lawns in the space of a morning. The process of emptying the vacuumed grass is the most strenuous and should only be tackled by someone in good health and good physical condition. If you are unable to physically participate, think about putting a out a cooler with lemonade or soft drinks; you could also offer the workers a few dollars to defray the cost of gasoline.