Thatch and the Healthy Lawn

"So this is the thanks I get," says one homeowner after another. We fertilize and agonize over our lawns until they are a bright, shiny emerald green, and then in just a few short years they are brown and full of bare spots.

Homeowners panic. It is disease? Is it rot? Is it rodents? Actually, it's thatch, the by-product of a healthy lawn.

Grass has two parts that appear above ground. The green blade is the most well known. The woody section is composed of the same elements found in the wood of a tree and grows about one inch above the soil, holding the blades upright.

Mowing the grass cuts the blade, not the woody section. These clippings can be left on the lawn because they disintegrate quickly.

The woody section does not deteriorate rapidly and over time can build up and create thatch. By pushing our lawns with fertilizer, the woody section develops more quickly, speeding up the thatch creation process.

The woody section breaks down when certain bacteria are present. These bacteria function better with adequate air and nutrients. As thatch develops, air cannot circulate through the woody layer, thereby escalating its own destructive process.

Less than a half-inch needs attention.

De-thatching physically opens up the sod to air movement, which will allow for proper decomposition. Generally, a de-thatching machine is used, which reaches down just below soil level, cuts through the thatch and raises it to the surface. From there it is removed by raking and more raking.

Generally, the lawn does not need reseeding or fertilizing after de-thatching unless it is badly patched with brown spots.

Most homeowners enjoy their lush lawns and don't want to forfeit its good appearance just because taking good care of it will lead to thatch. If they plan to continue to treat their lawns well, they should plan on core aeration every year to help prevent thatch from developing.

Core aeration creates one half inch or more diameter holes about four to six inches apart in the soil, and if the soil is moist enough, the holes could be up to 3/4 of an inch to 1/2inch deep. This allows air circulation within the lawn and soil, providing better deterioration of the woody section. Once removed, the cores should be left on the surface of the lawn to decompose, as they contain the bacteria for decomposition of the woody thatch material.

Core aeration and de-thatching machines are available at your local nursery or garden center.

Thatch is a normal occurrence in a healthy lawn. Its appearance does not mean the grass is diseased. However, without proper de-thatching or core aeration, the yard could lose its green luster and eventually die, or become completely debilitated.