How to Dethatch and Aerate Your Lawn

As fall fades into winter, it's time to combat two common lawn enemies: thatch and soil compaction. Thatch is the buildup of dead organic matter and, along with compacted soil, it can prevent your lawn's roots from getting enough water and air. Dethatching and aerating your lawn each fall helps your grass thrive come spring.

Thatch builds up when grass clippings are not chopped finely enough with a mulching mower or if excessive clippings are not removed after cutting. To prevent thatch from accumulating, rake your lawn after mowing, especially at the end of the growing season. If you've got thatch buildup, you might need to dethatch.

Step 1: Dethatch

Dethatch your lawn. Dethatching is an important component of lawn maintenance. You should dethatch if thatch is more than ½" thick. Use an iron rake or a thatch rake to cut through and rake off thatch. This will also scarify the surface. For large lawns, you may want to consider renting a walk-behind dethatching machine.

Contrary to common homeowner practice, you should never dethatch in mid- to late spring or during your lawn's active growing season. Because it exposes the soil, dethatching can give weeds a chance to take over your yard. Instead, dethatch your lawn in the fall after growing season.

Step 2: Check for Soil Compaction

Check your lawn for soil compaction. Over time, soil can also become too compacted for water and air to penetrate. Soil compaction can be caused by heavy foot traffic, vehicle traffic, dry weather, slow drainage and water logging. "Browning" of your grass can be a sign of compaction. You can also test for compaction by watering your lawn, or wait for a good rain, and observe how quickly the water is absorbed. If it isn't absorbed quickly, the soil is compacted. Or check for soil compaction using a wooden matchstick. You should be able to easily press the matchstick all the way into the ground with your thumb. If you can't or it hurts your thumb to try, your soil is compacted.

Step 3: Aerate or "Spike" Your Lawn

Aerate your lawn. Lawn aeration is a perfect solution for soil compaction. For moderately compacted soil in a limited area, systematically prick holes in the soil with a spading or digging fork. Holes should be 2" to 3" apart and 1" to 2" deep. If you're dealing with a larger area or you want to make the task easier, there are several types of push spike aerators you can rent or purchase. Some models look a little like a manual push mower with spikes or star-shaped wheels instead of blades. Others are designed as attachments that fit behind a power mower. For medium to large areas, you'll want to rent a gas-powered spiking aerator.

Lawn aerating is generally easier to do when the soil is moist, but it won't work as well if the ground is wet.

If you're wondering when to aerate, it's best to do it in the fall after dethatching or after a thorough raking.

Step 4: Create Larger Holes

If you have severely compacted soil, you need to open up deeper and larger holes. A spading or digging fork will do the trick if you have sandy soil or a small yard. Use the same systematic approach as you would for pricking, but drive the fork into the ground about 3" to 4" and wiggle it back and forth to open the holes.

You can also use a hollow-tine fork, another lawn aerating hand tool available for purchase or rent. A hollow-tine fork is stepped on to drive it into the soil, and when removed it pops out multiple cores or plugs of sod and soil. For medium to large areas, you may want to rent a gas-powered plugging aerator.

You can prick or spike the soil annually, but don't cut plugs more than once every three years. You can leave the plugs on the lawn because they break down quickly. Or rake them up and add them to your compost pile.

Good job! Now that it's been properly dethatched and aerated, your lawn should thrive in the spring.