Thatch is organic debris built up on the surface of the soil in your lawn. As your lawn grows, it sloughs off dying stems, rhizomes or stolons, as well as grass blades and roots. Along with insects and bugs, the organic debris forms a layer of decaying matter that covers the soil's surface. Too much thatch, though, and you have to remove it; this is called dethatching.
A thin layer of thatch acts as a kind of compost; the decaying debris eventually breaks down into the soil and replenishes the nutrients. Thatch is a part of the growth cycle of your lawn. Some species of grass, though, produce an abundant amount of thatch, such as Bermuda grass and Kentucky Blue, but any lawn is susceptible to excess thatch due to overwatering, over-fertilization, excess rain or if it becomes overgrown.
A layer of thatch more than one or two inches in thickness may negatively affect the growth of grass. It prevents water from reaching the soil surface in sufficient quantities and reduces exposure to sunlight. Applied fertilizer is absorbed by the organic materials, further feeding the thatch rather than the lawn.
A metal rake may be sufficient to remove enough of the thatch to prevent damage to your lawn. Rake your lawn using short strokes and gently pull up any thatch caught by the rake's tines. Because thatch is beneficial to your lawn in appropriate amounts, you do not want to completely remove it.
By removing only the thatch that comes away easily from the soil's surface, you're dethatching the lawn without damaging healthy root systems or the soil itself. Thatch that is breaking down and composting into the soil should be left to complete the cycle.
Distressed lawns may require more drastic action. If the layer of thatch is more than three inches, a power rake may be needed. A power rake is equipped with blades that move vertically to the surface and slice the thatch, rather than pull it up. This breaks down the layer of debris, hastening the decomposition process. You do need to rake up the thatch afterward, however.
One of the side benefits of dethatching your lawn is that the thatch is an excellent source of carbon for your compost heap. After dethatching, gather the thatch and place it in your compost heap. Primarily made up of yard waste, the thatch is a compostable material that breaks down into a nutrient rich compost ideal for vegetable gardens.