Grass & Grass Seed
How to Aerate & Dethatch Your Lawn
Too much thatch can weaken your lawn. You have two ways to remove it: dethatching and aerating.
Thatch and Compacted Soil: 2 Problems You Can Fix
Over time, little bits and pieces of grass die and gather just above the soil. This is called thatch. A little bit of thatch can be beneficial. It's organic material that is broken down by microbes in the soil. But sometimes, thatch builds up too fast for natural processes to break it down. It forms a barrier, keeping moisture and air from going where your grass needs it. A half-inch or more of thatch can weaken your lawn. You have 2 ways to remove it: dethatching and aerating.
If your lawn doesn’t seem to be growing as well as it should, even though it’s being fed regularly, it may be because of either thick thatch or compacted soil (or both). In both cases, the grass is suffering because air, water, and nutrients aren’t able to move freely into and through the soil, and are having trouble reaching the roots. You can tell your soil is overly compacted if you can’t easily insert a screwdriver into it. When thatch (bits of grass that have died and gathered just above the soil line) is too thick, your lawn will feel spongy, and it will be difficult to stick your finger through to the soil.
Either way, you need to take action. If your lawn’s failure to thrive is due to compaction, you will want to aerate it. If thick thatch is the problem, you will instead need to dethatch your lawn. Here’s how to do both of these simple fixes.
What Is Lawn Aeration?
Lawn aeration, coring, and aerifying are different terms you might hear for the same procedure. A core aerator removes plugs of soil from your lawn, which helps loosen compacted soil and allows vital air, water, and nutrients to reach the roots. You can either aerate your lawn yourself or call a lawn service. If you plan to DIY, rent an aerator (you’ll need help and a truck to transport it) and follow these tips.
How to Aerate Your Lawn
- The day before aerating your lawn, apply 1 inch of water to the lawn to soften the soil.
- Make sure to mark any sprinkler heads or shallow irrigation, septic, or utility lines so that you won’t accidentally run them over.
- For lightly compacted soil, go over your entire lawn once with the aerator, making sure to follow directions for use.
- If your soil is seriously compacted (or if you’ve never aerated it before), go over the entire lawn twice, with the second pass perpendicular to the first.
- The aerator will remove plugs of soil. Leave them on the lawn so they can break down and add nutrients back into the soil.
- Once you’ve finished aerating the lawn, water it well.
- Apply Scotts® Foundation Soil Improver to help strengthen, further alleviate compaction, and improve the structure of your soil. Then follow up with an application of Scotts® Turf Builder® Lawn Food to provide the nutrients needed to help the lawn recover. (Need a spreader to apply the fertilizer? Check out our article on How to Choose Lawn Products and Spreaders.)
- Water your newly aerated lawn every 2-3 days during the next couple of weeks.
When to Aerate Your Lawn
You want to aerate the lawn when your grass is in its peak growing period so it can recover quickly—think early spring or fall for cool-season grasses, and late spring through early summer for warm-season grasses. If you have high-traffic areas or heavy clay soil, you will want to aerate every year. If you have sandy soil or your lawn is growing well, aerating the lawn can happen every 2-3 years.
What is Dethatching?
Thatch is a layer of living and dead grass shoots, stems, and roots that forms between the green grass blades and the soil surface. Some thatch (1/2 inch or less) is actually beneficial; it acts like mulch to provide insulation from temperature extremes, helps keep moisture in the soil, and provides a protective layer of cushioning. However, when the thatch layer is more than ¾ inch thick, it can lead to increased pest and diseases problems (and reduce the effectiveness of some fungicides and insecticides), and reduce the amount of oxygen and moisture that are able to reach the soil and grass roots. When this happens, it’s time to dethatch your lawn. Dethatching removes this thick layer of decaying plant material so air, water, nutrients, and fertilizer can reach the soil better, plus your lawn can drain more effectively.
You can hire a lawn service to dethatch your lawn for you or follow these steps to do it yourself.
How to Dethatch Your Lawn
- Small lawns can be dethatched using a specialized dethatching rake, or you can rent a dethatcher (also known as a vertical cutter, verticutter, or power rake) to tackle larger lawns
- Mow your lawn to half its normal height before you begin dethatching.
- Using a dethatching rake is similar to using a regular rake. The tines dig into the thatch and pull it upward helping to loosen and remove thatch. While you rake, you should feel and see the thatch separating from the soil.
- If you’re planning to use a dethatcher, be sure to mark any shallow irrigation lines, sprinkler heads, or buried utility lines before starting.
- When renting a dethatcher, be sure to ask the rental agency to adjust the spacing and cutting depth for your grass type before you leave. The blades should be set to cut no deeper than ½ inch into the soil. Also ask the agency for directions regarding how to use the dethatcher, then follow them carefully. A dethatcher is heavy, so be sure to ask someone to help you load and unload it, and know that you’ll need a truck to move it.
- After dethatching, your lawn will look ragged. Rake up the loosened thatch and remove it from the lawn.
- If bare spots were created by dethatching, use a patching product, like Scotts® EZ Seed®, to repair them.
- Fertilize your lawn after dethatching to help the lawn recover. Do not fertilize before dethatching.
- Keep your lawn well-watered to help your grass recover.
When to Dethatch Your Lawn
The lawn should be dethatched when it is actively growing and the soil is moderately moist. The best time of year for dethatching is the same as for aerating: early spring or early fall for cool-season grasses, and late spring through early summer (after the second mowing) for warm-season grasses. That's when your grass is growing most vigorously.