Question: I think I have thatch in my lawn. Should I use a dethatcher, and when? Why does thatch form?

Answer: Thatch is the layer of undecomposed organic matter that develops on top of the ground and under grass runners. Given time, it can become impenetrable to water and nutrients, almost like a piece of thick canvas. Don’t confuse thatch, however, with the dried stubble that a lawn has after a cold winter. Those are just old grass blades that are standing in place. Bermuda is most likely to have a layer of thatch, and your first evidence will be random areas that just don’t seem to respond to fertilizer and water. They’ll often be in sunny spots, where the grass has grown very actively in the past. You may even detect a spongy feeling when you walk on those areas. If you suspect thatch, take a square-bladed shovel and dig a piece of sod. If there is thatch, you’ll be able to see it beneath the runners. Use an aerifier that actually pulls plugs through the thatch and out onto the top of the lawn to help eliminate the thatch. Dethatchers work, but they also tear away at the runners, not good for the vigor of the grass. Dethatching is a spring job, but aerifying can be done at any time. St. Augustine is less likely to form thatch. Hybrid bermudas seem to be the worst. Avoid high-nitrogen, quick-release fertilizers, and mow your lawn frequently so the grass clippings will be comparatively small. Both practices will lessen potential of thatch.