My neighbor had his lawn power raked this spring. Should I have my lawn power raked?
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– Bob Jefferson, Barrington
I prefer using core aeration as an annual cultural practice for lawns. Power raking can be beneficial for lawns that have excess thatch buildup (more than 3/4-inch thick). Combining core aeration with proper watering, mowing and fertilizing practices will help keep your lawn growing strong and better able to withstand stress and reduce weed problems.
The best time to aerate cool-season grasses like Kentucky bluegrass, which makes up most Chicago-area lawns, is in spring and fall, when the grasses are actively growing. Weather conditions are different from year to year, but April and May or September and October are generally good months to schedule aeration. I prefer the spring window for core aeration, although aerating twice a year can be beneficial for lawns that are heavily used.
Core aeration improves the lawn’s health and vigor by breaking up soil compaction, which improves water drainage, nutrient absorption and air circulation to the roots. A stronger root system promotes a better-looking and healthier lawn.
Lawn aeration also helps to decrease the buildup of thatch, which is a layer of organic matter that has not decomposed at the top of the soil. This can occur when there is excess grass growth caused by over-fertilization and light, frequent irrigation.
If this layer gets too thick, it will absorb moisture and encourage shallow rooting of the grass, making it more prone to drought stress and less able to absorb nutrients. Grub control is less effective when there is excessive thatch in a lawn. Lawn aeration also provides an opportunity to overseed if any areas of your yard are thin.
Core aeration is done with a machine that removes small plugs of grass and soil from the ground. You will get the best results if the soil is moist but not wet — the machine is not able to pull good cores if the ground is very dry and hard.
You can rent a core aerator or hire a company to do the work for you. The machines are heavy and easiest to transport in the back of a truck. Flag any sprinkler heads, light fixtures, valve boxes and other hidden items before aerating so that you can avoid damaging them — or the machine — while aerating.
If your lawn has been recently sodded, make sure it is well rooted in before aerating, or the machine will pull up the sod. A general rule is to wait a year after sodding before beginning a core aeration program.
It is best to leave the cores on top of the lawn and let them naturally break down over a couple of weeks.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at [email protected]. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.