Dethatching Techniques

Causes

• Although many people believe that grass clippings contribute to the problem, the main components of thatch are grass stems and roots. Moisture-rich clippings break down too quickly to form thatch, according to the University of Illinois Extension. Grass stems and roots break down much more slowly, so they accumulate faster than they decompose. Maintenance practices, such as excessive fertilizing and watering, contribute to thatch development because those practices encourage the grass roots to grow too rapidly. Failure to aerate a lawn also promotes thatch development because it allows the soil to become dense and unable to provide adequate water and air movement to the grass roots.

Core Aeration

• Proper core aeration helps relieve soil compaction and allows grass to develop thick, healthy roots. Many aerators available for rental or designed to roll behind a garden tractor will not provide effective aeration, according to Purdue University Extension. They may not penetrate the ground deeply enough or create enough holes. Purdue recommends using an aerator with reciprocating arms, capable of punching holes at least two inches deep and 20 to 40 holes per square foot.

Dethatching

• You can mechanically remove thatch with a dethatching machine. A professional lawn care company can provide this service or you can rent a machine. Purdue University Extension suggests that the most effective machines use knives or blades to tear the thatch loose and bring it up to the surface. Less effective machines have flexible, rake-like devices that attach to a mower blade. A heavy layer of thatch will require multiple passes with the dethatcher. Once the thatch is brought to the surface, you must rake it up and remove it from the lawn. If the thatch layer is thicker than one inch thick, you may have to use a sod cutter to remove the entire soil surface. You will then have to reestablish the turf.

Destructive Dethatching

• Mechanical dethatching can be destructive to your lawn, according to the University of Illinois Extension. Once thatch has developed, your grass roots actually grow more in the thatch layer than in the soil beneath it. By ripping out the thatch, the roots are damaged and the grass plants tear out easily. If you do dethatch, overseed your lawn with new grass seed. For this reason, dethatch in late summer or early fall, the best time of year for new plants to take root.