Thatch is a layer of living and dead organic material that can build up underneath the grass stems. Some grass types are more susceptible to thatch than others; however, all lawn grasses can build up excessive thatch if over-fertilized, over-watered and under-aerated. Excessive thatch buildup of a half inch or more causes poor grass health because the grass roots no longer are embedded in the nutrient-rich topsoil. Instead, the grass roots are only able to anchor into the layer of thatch buildup. Core aeration is the primary method of control and prevention of excessive thatch.
Rent or purchase a core aerator from a lawn and garden store. Core aerators mechanically puncture small holes or cores into the topsoil at fixed intervals.
Water the lawn two days prior to aeration with at least one inch of water. Moist topsoil is easily aerated and reduces the recovery time of the lawn grass after aeration.
Guide the core aerator over the entire lawn surface. Aerate each section of lawn from two different directions to ensure complete coverage.
Leave the cores of topsoil on the lawn. The cores are nutrient-rich and typically break down into the topsoil within two to three weeks.
Allow the lawn to fully recover over the next two to three months, and then evaluate whether more aeration is needed. Healthy lawns should be aerated once or twice a year, whereas thatch-prone lawns may need to be aerated more frequently.