The Most Important First Step In Your Lawn Overseeding Project

If your lawn is looking patchy, thin, and worn, figuring out a way to fix it can be a challenge. In many cases, the relatively inexpensive practice of overseeding your lawn can do the trick. It can help thicken the look of your grass, fill in bare spots, and restore a vibrant green color. But the very best way to overseed your lawn includes preparing it properly to ensure that the new seeds germinate. That's why the most important first step in overseeding is dethatching or aerating the lawn. This removes any barriers that might prevent the grass seeds from reaching the soil and promotes healthy root growth for a lush, green lawn.

Overseeding is the process of spreading new grass seed over an existing lawn. It isn't the same as re-seeding, because you don't rip up or remove the old grass. Instead of starting from scratch, overseeding is a way to fill in and improve upon what's already growing. Because you're leaving the established grass in place, it's essential to dethatch as needed to give the seeds the best shot at growing successfully.

Not sure what it means to dethatch a lawn? Over time, a layer of dead and living organic material, such as grass blades, leaves, and twigs, builds up on the soil surface of your lawn. A thin layer of thatch — one that measures 1/2 inch or less — is good for your grass. However, a thicker thatch layer prevents grass seeds from reaching the soil and keeps roots from getting the air, moisture, and nutrients that they need for healthy growth. When you remove the thatch — or dethatch your lawn — before overseeding, you'll ensure that the seeds you spread reach the soil. 

For a small lawn, a metal dethatching rake can work well to remove the layer of dead grass, twigs, and leaves, and loosen up the soil for overseeding. However, if you have a larger yard, a power rake is a more efficient option. This engine-powered tool uses revolving tines to remove the thatch.

After you've dethatched the lawn, the next step before overseeding is aerating the soil. This is only necessary if you haven't aerated the lawn in the past year or if your soil is compacted. To determine whether your soil is compacted, push a screwdriver into the first couple inches of soil. If you encounter resistance, the soil is compacted.

While dethatching should be your first step in an overseeding project if your lawn has a thatch layer thicker than ½-inch, it isn't necessary for thinner thatch layers. In that case, aerating the lawn alone to loosen it is usually sufficient to prepare it for spreading your new grass seeds.

A core aerator is usually the best tool for the job, especially if you have a large lawn. You can rent one at most hardware and garden supply stores. It has a series of hollow tines that remove cylindrical plugs of soil as you run it over the lawn. Before overseeding, use the core aerator to go over your soil three to four times, creating 20 to 40 holes per square foot of lawn.

The aerator leaves the plugs on the surface of your lawn, but you should break them down a bit before overseeding. Use a garden rake to break them and distribute them evenly across your lawn. When you spread your grass seeds, they will have excellent contact with the loosened soil, making successful germination more likely.