A healthy lawn is more than just aesthetically pleasing. Well-maintained lawns decrease water run-off, lower soil surface temperatures and may even raise home values, according to Cornell University. Aerating and dethatching are two steps in a total lawn maintenance program. Combined with proper fertilizing, watering and mowing, they keep lawns looking green and healthy.
Dethatching is the process of removing thatch--decomposing grass and roots--that form a thick mat at the base of the soil.
Aerating is the process of punching holes into compacted soil, loosening it up and allowing moisture, oxygen and nutrients to reach the grass roots. Aeration is the best way to prevent thatch buildup, according to Cornell University.
A thin layer of thatch--less than 1/2-inch--is healthy for lawns, according to Cornell University because it may protect plant crowns and reduce soil compaction. Thicker layers of thatch, though, may cause water to run off, rather than penetrating the ground, resulting in yellowed, dried spots. Once saturated, the thatch may also suffocate grass roots. The best way to determine if thatch is a problem is to insert a finger into the lawn to feel the matted surface next to soil. Thatch thicker than 1/2 inch is best removed.
Turf experts recommend annual aeration for heavy clay soils or those that may become compacted through heavy foot traffic, according to "Sunset" magazine.
A thatching rake is a rake with long, sharp tines. Homeowners rake the tines through the grass, removing thatch and discarding it. Dethatchers, or vertical mowers, are a better choice for large lawns. They have revolving blades that dig into the soil, removing thatch. Dethatchers are available for rental at hardware stores. Dethatchers or power rakes may damage lawns and soils, however. University of Rhode Island Landscape Horticulture program recommends hiring a professional and not dethatching wet lawns.
For aeration, renting a gas-powered aerator machine or hiring a professional is usually best. The barrel of the machine has corers that punch small plugs of soil out of the ground. Dethatch and aerate cool-season grasses in the fall and warm-season grasses in the spring.
While aeration is recommended annually, only dethatch when absolutely necessary. Try other methods, such as aeration and good cultural practices first.
Dethatching allows moisture and nutrients to reach the grass roots, building healthier plants. Additionally, removing thatch prevents diseases from building up.
Aeration promotes healthier soils, which in turn, produce healthier grass. Oxygen, moisture and water more easily reach grass when the soil isn't compacted. Unlike dethatching, aeration doesn't damage grass roots and there is no risk of digging too deeply into the soil.
Good cultural practices may minimize thatch buildup. University of California Integrated Pest Management Online recommends watering deeply, rather than shallowly, and mowing lawns at the proper height for the lawn variety. Leaving grass clippings on the ground generally doesn't cause thatch, according to Cornell University, but excessive fertilizing, especially in the spring may cause thatch.
Amending the soil before planting seed is the best way to improve compacted soil. Even with good soil preparation, heavy clay soils may need annual aerating.
- Cornell University Gardening Resources: Relieving Thatch
- University of California Integrated Pest Management Online: Dethatching Methods
- Sunset: Dethatching and Aerating Your Lawn
- Cornell University Gardening Resources: Why Lawns Matter
- University of Rhode Island Landscape Horticulture Program: What is Thatch?