You might have heavy clay soil which compacts easily, or perhaps you have a ton of children (or adults) running all over your lawn. Maybe you had construction work done with heavy equipment parked on the grass. Or maybe the grass has thinned or you’re transitioning to a low-maintenance native grass and wish to overseed your lawn. So you decide to aerate your lawn. But what do you do after?
After aerating your lawn, leave the plugs and open holes alone, top-dress with compost, overseed, and water as needed. Avoid mowing and spraying herbicides and pesticides, whether synthetic or organic, on germinating or seedling grass.
Table of Contents
- 1 Step-by-Step: What to Do After Aerating Your Lawn
- 2 Lawn Aeration Frequently Asked Questions
What is Lawn Aeration and When To Do It
A core aerator cuts out plugs of grass and soil throughout your lawn. These new holes relieve compaction by giving grass room for their roots to grow and oxygen to breathe (yes, roots need oxygen too!), and allows water to sink through the soil to reach the roots instead of puddling or running off.
Aeration is best done in the spring or early fall for cool-season grasses, and in the spring for warm-season grasses. You do not need to core aerate every year! Machine rental and hiring landscapers is expensive, and you only need to aerate when your lawn is compacted or you plan to overseed.
Step-by-Step: What to Do After Aerating Your Lawn
Step 1: Leave the plugs and the holes alone
After core aerating, you’ll have grass and dirt plugs scattered over the lawn. Leave them where they are. After a couple of weeks, they’ll have fully broken down, returning up to 25% of the grass’ nutrients [PDF] back onto the soil.
Also, don’t fill in the holes with anything. I’ve seen some people suggest filling them with sand, but that seems like the exact opposite of what you’re trying to do — to relieve compaction. Like the plugs, the holes will disappear on their own, either by old grass spreading or new overseeded grass growing.
Step 2: Top-dress with compost
The open holes in your lawn make it easier for compost to reach the soil, where the beneficial microbes in the soil will break down the compost into nutrients for your grass. Use a broadcast spreader to add a 1/4-inch layer of compost over your lawn. Roll the spreader over the lawn at different angles to ensure even coverage.
Avoid chemical fertilizers. They may seem like a better option but they actually strip the organic matter from the soil (making your lawn utterly dependent on more fertilizers to survive) before the synthetic nitrogen runs off into nearby water sources becoming a pollutant. A ¼-inch topdressing of compost once or twice a year is enough nutrition and the compost supports the soil ecosystem rather than destroys it for healthier grass overall.
Step 3: Overseed
Now that you’ve got a nice ¼-inch layer of compost feeding your grass, it’s time to overseed. Chances are, you decided to aerate your lawn specifically to make room for seeding more grass for a thicker lawn.
Ideally, you’d overseed immediately after aerating and top-dressing, but you can also wait a day if need be.
But don’t wait too long. You just opened up a lot of bare soil, and if nature abhors one thing, it’s bare earth. Other plants will take advantage and grow. The ¼-inch layer of compost will help prevent weed seeds already in the soil from germinating, but more seeds can land on top.
Don’t cover grass seed with soil, but do tamp it down to press the seeds gently into the soil for firm contact. Grass seed needs light to germinate. If you forgot to top-dress before overseeding, then wait for the grass to germinate.
Step 4: Water Frequently
If you overseeded, then you need to water frequently to keep the soil moist for germination. This may mean as much as 2 or 3 times a day over the next 2 to 3 weeks. You may need to water even longer depending on your grass variety, as, for example, bluegrass takes longer than ryegrass to germinate. When the grass seedlings appear to thicken, then you can return to your regular schedule.
If you haven’t overseeded, then don’t change your watering schedule. Your lawn needs water when, after walking across it, you can still see your footprints. Less frequent, deeper waterings encourage more resilient grass, as the grass must grow roots deeper to access water. Shallow waterings mean that grass grows roots close to the surface, which spells bad news as soon as the summer heat sets in. The only time you should water more frequently is if you have sandy soil, as sand doesn’t hold on to the moisture as well as loam or clay soil.
Step 5: Hold Off On Mowing and Chemical Interventions
Hopefully, you remembered to mow before core aerating, because you’re going to have to wait a few weeks while the overseeded grass germinates and grows to 3 inches tall. This gives the seedlings time to set roots and grow strong before you run a lawn mower over them.
Also, try to hold off on heavy foot traffic. If you have kids or pets, keep them off the lawn for a few weeks. Too much weight will damage the seedlings.
And wait on applying any kind of herbicide or pesticide, whether inorganic/synthetic or natural. These seedlings are delicate. Even natural herbicides can apply too much stress on them. The best way to handle weeds is by hand-pulling. Experts advise waiting until you’ve mowed 4 or 5 times before applying anything.
Lawn Aeration Frequently Asked Questions
Can You Aerate too Much?
Yes, you can aerate your lawn too much. At most, only use core aeration once a year, and only on compacted soil or when you plan to overseed. Otherwise, you’re just damaging your lawn for no reason.
Should I Mow Before or After Aeration?
You should mow before aeration, and avoid mowing after aeration, especially if you overseeded. This gives your lawn time to recover before you cut off pieces. Grass seedlings are delicate and need time to grow roots before mowing.
If your grass is growing vigorously, cut the lawn much lower than you would normally, even down to 2 inches for cool-season grasses. Check beforehand that you won’t cut through the crown of the grass, the little part just above the soil from which the grass blade grows, or you could permanently damage the grass.
Is it OK to Aerate After a Rain?
It’s OK to aerate after rain. In fact, it may be to your benefit as aeration is best done when the soil is moist. However, you don’t want to be hauling heavy equipment (and a core aerator is heavy!) over your water-logged lawn as it will cause even more compaction. Heavy, waterlogged soil will be harder on the equipment as well.
How Long Does it Take for Aeration to Work?
The benefits of aeration should start pretty much as soon as you’ve core aerated, although it will take more time to see the results. Plugs will break down within 2 weeks.
Can You Just Sprinkle Grass Seed on a Lawn?
You could simply sprinkle grass seed on an open patch of dirt or on a lawn, but germination rates will be lousy. You’ll improve germination rates by mowing, aerating, and topdressing with compost, then using a broadcast spreader to lay the seed down at an even, consistent rate. Then press firmly into the soil, but don’t cover, as they need a bit of light to germinate.