Core Aeration of Lawns

Core aeration is a great way to improve the health of your lawn.  Aeration relieves soil compaction, improves water and nutrient movement in the soil, and prevents thatch accumulation.  Aeration improves the growing conditions for the turfgrass plants and results in a healthier, more vigorous lawn.   

Plugs of soil from core aeration Photo by Lost_in_the_Midwest
Core aeration pulls out small plugs of soil.  Photo by Lost_in_the_Midwest.

When to Aerate the Lawn

In Iowa, September and April are the best times to aerate Kentucky bluegrass and other cool-season lawns.  While the overall results are beneficial, core aeration causes some initial damage.  Aerating in September or April allows the grass to quickly recover during the favorable growing conditions in spring and early fall.   

How Often to Aerate the Lawn

The frequency of aeration is largely determined by the soil type and the amount of use.  Lawns growing in heavy, clay soils and those subject to heavy foot or pet traffic should be aerated twice a year.  Once a year should be sufficient for lawns that are established on well-drained soils and experience little traffic.  September and April are the best times to aerate Kentucky bluegrass and other cool-season lawns in Iowa.   

How to Aerate the Lawn

Aerate lawns with a core aerator.  Core aerators have hollow metal tubes or tines that remove plugs of soil.  Avoid spike-type devices that simply punch holes (compacting the soil) in the ground.  Core aerators are often available at rental agencies.  If you prefer not to do it yourself, core aeration is a service provided by most professional lawn care companies. 

Core aerator Photo by Atlantic_Advertising
Core Aerator.  Photo by Atlantic_Advertising

Remove soil cores that are approximately three-fourths of an inch in diameter and 3 inches long.  For best results, aerate lawns when the soil is moist.  Avoid aeration when soils are dry or wet.  The tubes or tines will not be able to penetrate deeply when the soil is dry and may get plugged with soil when the soil is wet.   Lawns that are properly aerated should have 20 to 40 holes per square foot.  Since most core aerators won't remove the proper number of holes with a single pass, several passes are often necessary.  After aeration, pull a drag mat or weighted piece of fencing material across the lawn to break up the soil cores on the soil surface.

After Aerating the Lawn

To help promote recovery of the lawn, fertilize the lawn one week prior to aeration and irrigate the lawn after aeration if the weather is dry.  Overseeding and fertilizing can also be done after aerating the lawn.

Aerating and Compost

Compost can be used as a top dressing on lawns to help improve soil quality.  Applying a thin layer (1/4") of fine compost along with core aerating is one of the best application methods.  Spread a thin layer of compost using a shovel and work it into the turf with a leaf rake.  Then core aerate the lawn and use a drag mat to break up the cores and mix in the compost.  

Last reviewed:
April 2023