De-thatching a Lawn
Thatch is a compressed, light brown organic matter that looks like peat moss and is located between the soil line and grass blades. Thatch can be beneficial or detrimental, depending upon the amount present. Several problems will develop if a lawn has more than ½ inch thatch buildup. The biggest problem will be the lack of water penetration to grass roots. Water is repelled by thatch. Likewise, fertilizers and other chemicals can run-off or be caught in the thatch layer. Thatch provides a hospitable environment for disease and insects. Finally, excessive thatch will make the turf less cold, heat, and drought tolerant.
To tell if thatch has become a concern, use a knife or shovel to cut a small wedge of turf down to the soil line. If the thatch layer is more than ½ inch thick, the turf needs to be de-thatched.
A variety of methods can be used to de-thatch a lawn. Methods include hand-rake, power-rake, verticutter, and core aerator. These machines stress the grass. Therefore, lawns should be de-thatched only when conditions favor rapid turf recovery. For bluegrass, fescue, and ryegrass lawns, de-thatching is most desirable in March, April, and September. Zoysia grass and Bermuda grass lawns can be aerified from late May through July.
Other lawn improvement practices can be performed after de-thatching or aerifying. These may include top-dressing, re-seeding, fertilizing, and watering.
Thatch build-up varies among lawns. Some lawns never develop a thatch problem, while others become thatch-bound within a few years. A common misconception is that grass clippings cause thatch. This is not correct. However, you can prevent thatch build-up by minimizing watering and fertilizing and by proper mowing.