A yard that can breathe is going to produce a dense and healthy lawn, and one of the best ways to open up the soil without disturbing the grass in place is to core aerate it. Like other yearly lawn care activities, it requires some planning and coordination with other maintenance.
As for timing your aeration and mowing schedule, it’s usually best to mow before aerating the lawn to be sure the aeration process goes as well as it can and capture as many benefits of the project as possible. When you mow first, it gives you a chance to expose the surface and clear it off for the aerators to reach the ground most easily.
How Does Aeration Work?
Aeration opens up the soil to increased water penetration and airflow. Aerators come in different models: hand or fork aerators, push aerators, and tractor attachments that get pulled across the lawn. Hand tool aerators are good for small spot-aeration, but they aren’t practical for full-yard coverage.
Most aerators are core or plug aerators, which penetrate the ground and lift 2 to 3 inch cores. Core aeration is a popular method since it removes and displaces the soil, unlike spike aerators that don’t open up the ground like coring does. Spikes, or tines, pierce the yard, but don’t create divots. Coring leaves behind the core pellets, which can be left in place or used for other yard work.
Should I Mow Before Or After Aeration?
It’s generally recommended to mow before aeration, especially if you’re overseeding. That said, it won’t hurt the lawn if you mow after aerating if you aren’t laying down grass seed. Mowing first allows you to expose the soil before aerating. The surface level of the ground will be clear and easier to reach with the aerator. Mowing first will also allow you to rake up thatch before aerating, opening up more of the surface.
Some choose to aerate before mowing, in which case the cores will be left behind on the unmowed grass. In this case, you should wait a day or two before mowing to let the cores dry and either rake them up before cutting or leave them in place to be broken up and redistributed across the lawn.
This can dull your mower blades, but it won’t damage the lawn to mow after aerating. If the cores are too hard, don’t mow them over; just rake them up or leave them on the lawn.
Mowing After Aeration And Overseeding
When you aerate is a great time to overseed the lawn since it makes the soil porous. When you aerate before mowing, the divots might get compressed and filled with soil and grass clippings as you mow the lawn. This doesn’t create as favorable an overseeding environment since the divots that the seeds could otherwise firmly settle into may be collapsed, covered, or filled.
How Long Should You Wait To Mow After Aerating?
If you’re overseeding the yard, mow first, aerate, then overseed, and apply mulch and fertilizers. When aerating and overseeding, it’s recommended to cut the yard a couple of notches lower than usual to expose the surface of the ground. Since you want the seeds to germinate before mowing again, the extra length in cut will extend the regrowth period and put off your next mow an extra week or two.
In general, waiting about 3 weeks after aerating and overseeding will give the seeds time to establish, though the time will vary based on germination rate per grass type. If you’re not overseeding, you can keep to your regular mowing schedule.
Why You Should Water Before And After Aerating
Lightly water the lawn the day before you plan to core aerate. The ground will be denser, more easily penetrated by the aerator, and the cores will lift out easily. Dry soil might not grab as quickly, and it can crumble while being pulled out.
After aeration, the ground will dry out more quickly since the soil is more exposed to the open air. The lawn should be watered a little more than usual for a couple of weeks until the cores settle and the grass roots grow into the newly opened spaces. If you’re overseeding after aerating, you’ll have to give that extra amount of water to the yard anyway.
Topdressing aerated soil
For similar reasons that aeration helps with irrigation, it allows fertilizers to penetrate the surface, adding to the topsoil’s nutrient content. Topdressing is applying surface-level organic solids that build soil’s structure and quantity.
Applying materials like mulch, fertilizers, compost, peat, or biochar helps the grass grow in dense root systems and blade coverage. If your yard has a water retention problem, adding sand when the soil is exposed by core aeration can help with drainage and keep the topsoil moist, not wet.
When you apply organic materials that decompose, the groundcover nurtures the grass and seeds from germination to sprout by providing a moist, supportive, growing environment. This kind of groundcover will contribute to maintaining a well-aerated topsoil and prevent swift compaction from watering or rain, as the solids help with good drainage and oxygen retention.
How Often Should The Lawn Be Aerated?
Aeration is only necessary once a year, and over several years, this schedule will have your lawn in a consistently well-aerated condition. If you have very compact soil, like clay soil, you may need to aerate twice a year, spread out 6 months apart. Remember, aeration is good for the lawn, but it does disrupt the roots just enough to not damage them.
When Is The Best Time Of Year To Aerate?
The best time of the year to aerate is during the growing seasons when the grass will benefit from oxygen and moisture access. Roots will be able to heal quickly from the light disruption of aeration and fill in the empty spaces with new growth. On the other hand, aerating too close to, or during, dormancy can damage grass since the roots can’t divert energy to repair.
The three main growth periods of the year are:
- Early and mid-spring – You can start aerating the lawn after the last frost and once the ground has completely thawed during the cool-weather grasses’ spring growing season between April and May.
- Late spring and early summer – When the temperatures reach 75 degrees and above in June and July, warm season grasses will sprout and grow, going dormant at the end of summer.
- Late summer and early fall – Aerating the lawn during the cool-weather grasses’ fall growth can be done up to two months before the first frost, generally in September. Take care not to aerate too close to winter dormancy.
Should I Leave The Soil Cores Or Remove Them?
Some homeowners like to collect and store their cores for compost, gardening purposes, or filling holes in the yard as they appear throughout the year. The choice to leave the cores in place or remove them depends on the case, but in general, it’s recommended to leave the cores in the yard unless you’ll be replacing the lost soil. They’ll break down and reincorporate into the ground after some rain or a few waterings.
If you do leave the cores around the yard but want to mow after aerating, be sure to let them dry so they’ll break up more easily. This can dull your mower blades, so check on the sharpness of your blades afterward if you do choose to mow over the cores.