September is an excellent time to aerate lawns growing in heavy, clay soils and those subject to heavy foot traffic. Aeration relieves soil compaction, improves water and nutrient movement in the soil, and prevents thatch accumulation.
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.
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.