If you want a lush, green lawn this year, the soil needs air, water, and sunlight. Learn how to improve your lawn’s growing conditions with this breakdown on dethatching and aeration with landscape contractor Lee Gilliam and host Kevin O’Connor.
What is Lawn Thatch?
Lawn thatch is a layer of material that sits on top of the soil. It’s essentially last year’s lawn, along with some leaf litter and small twigs and sticks, that has laid down after the growing and become a thick mat that the new grass needs to grow through.
Pro Tip: According to This Old House Magazine, thatch is more than just dead grass on the surface—it’s a “thick layer of accumulated organic matter—dead stems, roots, and leaves—that prevents air and nutrients from reaching turf roots.” Dethatching is an annual job, best done in early spring for cool northern lawn grasses and late spring for warm-season southern varieties.
Why is it a Problem?
Thatch is a natural material, but it can prevent the lawn from performing its best. It blocks the nutrients from grass clippings, water, sunlight, and air from reaching the soil, which means none of those essential elements can reach the roots of the grass effectively.
How Do You Dethatch?
There are a couple of ways to effectively dethatch a lawn. The first is to use a special dethatching rake, which has stiff, curved tines that reach between the blades of grass and pull the thatch to the surface. The other option is to rent or purchase a dethatching machine, which looks like a lawn mower and reaches down into the thatch layer to pull it to the surface of the grass where it can be collected and removed.
Aeration Basics
Thatch isn’t the only thing keeping nutrients from the soil. Weight from snow, thatch, walking, and other factors can compact the soil, causing it to harden and choke the grass’s roots. Aeration solves the problem, creating holes in the soil for nutrients to penetrate the soil.
Pro Tip: Roger Cook, This Old House landscape contractor, explains how a core aerator works: “The gas engine drives these spikes down into the ground. As they revolve, they go into the ground, come out, and they pull out a casting, a piece of dirt, and it lays on the surface actually leaving a hole in the lawn.” Those holes allow air and water to reach roots that compacted soil had been starving.
How to Aerate
Aerating involves poking or punching holes in the soil, and there are a few options here, as well. One option is to wear aeration spikes that strap to your shoes and poke holes as you walk. While they work, they also compact the soil, sometimes compounding the issue.
A better option is to use a coring aerator. This machine looks like a large lawn mower or a tow-behind attachment with tines that poke down into the soil and remove plugs of compacted dirt, depositing them on the surface. This allows plenty of air, water, or nutrients to penetrate the soil and feed the roots.
Pro Tip: This Old House landscape contractor Roger Cook recommends making two passes with the aerator for best results. As he advises in This Old House Magazine: “I run the aerator over the entire lawn in one direction, then make a second pass at 90 degrees to the first. Immediately afterward, I top-dress the lawn with 1/4 to 1/2 inch of aged leaf compost.”
After aerating, leave the cores on the lawn rather than raking them up. As This Old House host Kevin O’Connor and landscape contractor Lee Rodrigues agree, the cores break down in a week or two and return valuable nutrients to the soil. As Lee puts it: “I like to leave it because that’s all still a lot of nutrients there.”
Resources
Dethatching
Lee uses a power rake or an electric dethatcher for dethatching large lawns quickly. These can be rented from big-box retailers or landscape equipment rental companies. For a cheaper option that works well for smaller yards, a thatch rake and a regular leaf rake to clean up the pulled-up thatch.
Aeration
Lee prefers a core aerator because it removes soil instead of just pushing it down and compacting it further into the ground. Machine aerators can also be rented. For a cheaper option for smaller lawns, spiked aeration shoes can work.
