D. Aerating Lawn

The aerating lawn business is booming. For good reason, it works. There are many benefits to lawn aeration and the results are easily noticed.

In this short module we are going to cover some basics, and hopefully answer all the questions you may have about aerating.

Why do we aerate? When to aerate? What value is there in aerating lawns?

Do-it-yourselfers can benefit from this information about how to aerate, and why they should aerate their lawns.

I'm sure you have probably seen aeration cores since you were a kid on the soccer field?

I never knew what they were until I actually started landscaping. Until then, rabbit droppings was a pretty reasonable explanation.

So what is core aeration, and why do we do it?

Over time, lawns can become heavily compacted with foot traffic, kids playing, and pets running around. Lawns can also build up excessive amounts of thatch, that can limit the amount of water and oxygen that can reach the soil and roots.

Lawn Aeration, (core aeration) is a way of removing plugs of soil and depositing them back on the ground to break down into the soil again. This relieves compaction, while allowing water and nutrients to penetrate into the soil more efficiently. It also helps control the amount of thatch build up.

From the science end of this, aerating lawn is like a mini composting system. The micro-organisms contained in the cores break down the thatch, turning it into nutrients for your lawn. The cores also feed themselves back into the lawn as a mixture of soil and nutrients.

The process is not done overnight, and having these new holes in the soil allows oxygen and water to reach deep into the root system. This makes it a great time for spreading fertilizer, over seeding, or spreading lime for those with acidic soils.

When to aerate?

Core aeration does cause a certain amount of stress to your lawn. This usually takes three or four weeks for you lawn to recover from, so aerating lawn at the right time is important. It is not something that a homeowner has to do on a yearly basis (although many do.)

It is an example of how being in tune with the needs of your lawn will help you achieve success. If your lawn is not heavily compacted, and the buildup of thatch is limited to less than ½ inch, than you may want to
leave it.

It is recommended to only do what is required according to the health and condition of your lawn. Core aeration is considered a form of preventive maintenance, but many people prefer to aerate once a year. This is a choice that you have to make.

If you have very poor soil, then lawn aeration, combined with topdressing can be a great way to improve your soil slowly over time. A heavy core aeration, and topdressing with a good loam or compost, will greatly improve heavily compacted soils. You may want to soil test the cores if you don't know the quality of your soil.

As with anything in your yard that penetrates into the soil (no matter how shallow it goes), you should make sure that you know where all your utilities are first.

Cable and phone lines can be very close to the surface, especially near the house. irrigation lines and lighting systems can also be a concern.

Have them marked or located if you can to ensure you don't hit them.

Other utilities are usually buried deeper, but it is always your responsibility as a homeowner to protect yourself.


Another controversial subject is when is the best time for yard aeration? We will give you both recommended seasons and why each season is chosen. Aerating lawn with warm season grasses will be covered after cool season grasses. These times can vary depending on your climate.

Aerating is also stressful on a lawn, so a period of recovery is important.


For cool season grasses, yard aeration is best in the spring with the return of active growth. Try to make sure it is done before peak growth time. This gives your lawn a chance to recover, and take advantage of the ideal late spring conditions for growth and root development.

This helps prepare your lawn for the stress of summer heat and drought. Lawn aeration at this time, can also be easier having a moist, loosened soil from frost heaves, melting snow and spring rains. The downside for lawns that aren't so thick, is that you can have increased crabgrass germination. In this case, aerate before you use a pre-emergent crabgrass control product.

It is a good time to overseed as well, giving the seeds good contact with the soil. If you do seed, make sure you choose a fertilizer that is right for the seeds. NO pre-emergents should be used with seeding. Pre-emergents will prevent grass seed from germinating as well as weed seeds. However, starter fertilizers are acceptable.

One more quick note on overseeding when aerating and topdressing. If your topdressing layer is ¼ inch or less, you can seed before the topdressing is put down. If your topdressing layer is inconsistent or too thick, seed after the topdressing is down. Try not to bury the seeds more than 1/2 inch at the most.

Late Summer Early Fall

This seems to be the preferred time for aerating lawn, giving lots of time to take advantage of the return of favourable growing conditions in the late summer (up to mid-September). Cool season grasses start to grow again vigorously. Aeration timed with a fall fertilization or overseeding, can be extremely beneficial in preparing your lawn for winter and spring.

If you are experiencing hotter than normal temperatures at this time of year (65F or 18C or higher), you should hold off until temperatures cool down. This will help eliminate stress on the lawn. This is not so much of an issue if you have irrigation.

A good thorough and deep watering is recommended a few days before you aerate. This will allow the equipment to penetrate into the soil easier. Don't aerate soaked soil.

Warm Season Grasses

Warm season grasses are actively growing from early spring right through the fall. The ideal time would be late spring early summer. Aerating lawn between April and May, will allow warm season grasses time to recover and flourish as they enter their most active growing season. However, care must be taken with aerating machinery as to not tear up certain warm season grasses that grow by stolons.

Can I aerate more than once a year?

Yes. It's possible, but remember that it is stressful on a lawn. If you have a heavily compacted soil or a thick layer of thatch, you may need to aerate in the spring and summer for multiple seasons. (Sports fields frequently do this.)

Aeration machinery is only going to cover a small percentage (around 10%) of your lawn each pass. You should make two passes to make it effective.

Are the cores an issue for you? Rake them up and compost them if you want, but it is usually more beneficial to leave them. Also, don't compost them if you have spread any pre-emergents or weed and feed in the last month or so. 

Sandy soil and spike aeration 

Aerating lawn is generally more productive with a core aerator than a spike aerator. The only exception to this rule is for sandy soils. Sandy soils can also build up thatch, but rarely ever get compacted like a clay soil does. Spiked machines or shoes are effective for aerating lawn in sandy soils. 

It's time to learn about...Dethatching.


Table of Contents: Lawn Care and Maintenance

Introduction: Lawn Care and Maintenance

A. Watering

B. Mowing

C. Fertilizing

D. Aerating

E. Dethatching

F. Topdressing


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