Roots of grass and trees need adequate oxygen to function and be healthy. In fact, the optimal percentage of oxygen levels in the soil is similar to the air we breathe! Heavy or compacted soils, thick turf roots or thatch build-up, and even over-watering can starve roots of critical oxygen.
Core aeration is recommended at least once per year (spring or fall) when the soil is moist enough to be able to pull up a 2-inch plug of soil. The holes created allow air and water to penetrate into the root zone for healthier roots. Leaving the soil plugs on the surface allows them to break down and replenish the soil. If your topsoil is lacking organic matter, rake compost or other fine mulch over the turf surface after core aeration has been completed to fill in the holes.