Aeration – Why and how often?

Written by Ryan Such

“What’s the difference between aeration and aerating?” A customer recently asked me. The answer is:

Grammatically, aeration is a noun and aerating is an active, present progressive verb.

Operationally, which is what I assume the customer was asking, is nothing. There isn’t a difference. Aeration is the completed operation once we have aerated a lawn.

So why aerate, or get an aeration?

Aeration is the process of supplying air to the soil. Grass roots need air not so dissimilarly as we do. We supply air to the soil by pulling out cores of turf (that resemble delightful goose turds) and allowing those cores to slowly break down and return to the turf. As we pull cores out, that reduces the compaction of the soil, which in turn allows air to get to the roots. The reduction in compaction also allows water and nutrients to get directly into the root system, allowing for healthier grass.

When should you aerate?

While there is no bad time to aerate, the process is best performed in spring (May) or in the fall (September) when root development is the most active. Make sure to have a drill style aeration performed. Some providers still use roll style aerators that don’t plug the lawn very well.

How often should you aerate?

In our clay-based soil in the Red River Valley, people tend to aerate too little and want to power rake too much. Golf courses aerate a couple times a year and residential lawns should look at aerating at least every other year. This depends on soils, traffic and moisture but every other year is a good general rule.

Aeration can also pave the way for significantly increased lawn thickness by creating the perfect canvas for overseeding. This is the process of adding grass seed into an existing lawn. If we overseed immediately after aerating, the new seed gets direct seed-to-soil contact. It is an easy way to improve the density of the turf, establish improved grass varieties, enhance a lawn’s color and protect against weed infestation. It is recommended to fill in a lawn with 50% or more grass coverage. However, at 50% you will likely need overseeding twice to get the lawn to 90-100%. Just throwing seed on your lawn without aerating or working up the soil will have little to no positive effect on your lawn. Aeration prior to overseeding will increase germination rates substantially.

To prepare your lawn for aeration and overseed the lawn should first be sprayed to kill off any broadleaf weeds. The lawn should be mowed the day before or the day of, at the normal height, and any sprinkler heads should be marked. Core aerators love to eat up sprinkler heads.

The BE REAL Moment: Success of aeration and overseeding depends exclusively on the aftercare. Once aerated and overseeded, the lawn should not be mowed for 2-3 weeks and no herbicide should be applied for at least 5-6 weeks. The sprinkler system should be set to run 3 times per day for 3-5 minutes, depending on zones (mist heads 3 minutes and rotor heads 5-6 minutes). The goal is not to soak the lawn but to keep it moist. We recommend switching to a regular watering schedule 6-8 weeks after overseeding. If you do not plan to water the lawn, please temper your expectations of success.