What is Core Aeration?
Core aeration is a method whereby a machine (a lawn aerator) with hollow tines mechanically removes plugs or "cores" of soil and thatch from a lawn. Core aeration reduces soil compaction, creating a channel through which oxygen, water, and nutrients can penetrate the soil.
Why is Core Aeration Necessary?
Picture the soil under a healthy lawn. It's a soil studded with networks of air pockets. Oxygen travels through these pockets, and that's important: Just because grassroots are underground, that doesn't mean they don't have to breathe! But it's more than just oxygen that must percolate down through the ground, as your grassroots also need water and whatever nutrients homeowners are supplying when fertilizing lawns. There's a veritable beehive of activity going on down there under a healthy lawn.
Now consider the soil under the grass that is performing poorly. Instead of being fluffy enough for oxygen, water and nutrients to flow through it (down to the grassroots), it is compacted. It may also be crowned with a thick layer of thatch, rendering it even more impervious. This lawn is crying out for core aeration.
What's the Best Time for Core Aeration?
For cool-season grasses, perform core aeration in early fall. For warm-season grasses, the time generally recommended for core aeration is mid-spring to early summer.