Thatch is a buildup or organic matter that is between the lawn and the soil. This can be any type of vegetation. The main component is normally grass clippings. Bagging or mulching lawnmowers don't tend to cause much thatch, but the old fashioned side discharge lawnmowers can cause a lot of thatch.
Thatch is natural â€¦ well as natural as anything that comes from something as unnatural as a lawn can be. It tends to start innocent enough. You mow, you ignore the grass clippings, and in a few years you end up with this dry mess of clippings that are causing all your watering and fertilizing to be for nothing.
A nice thin layer of thatch is helpful to a lawn. It protects the soil and grass roots from the drying effects of the sun and wind. As it accumulates (as things do when ignored) it starts to become a problem. When it is less than 1 inch thick it can make a nice mulch. Just like the mulch you put in your flower beds. It works on the same principal as that mulch as well. It conserves water by shading the soil.
The day always comes. The day you discover that your thatch has become more of a hindrance than a help. You find that your lawn is turning brown, even though you water it. The grass that used to need mowing every 4 days is suddenly growing at a sluggish pace. You start finding brown patches where your thick green lawn used to be. The time has come to dethatch your lawn.
Dethatching a lawn isn't a pretty process. It's not that hard but it is messy. If it is not already part of your normal lawn care routine you should start scheduling it in. You can core aerate to bring good bacterial up from the soil to eat up the thatch, or you can go and pick up a dethatching rake. If you core aerate once or twice a year you don't have to do the raking, but if your situation is dire you might just have to bite the bullet and start ripping the thatch out. If you know how to dethatch a lawn you are good to go. If you don't you might want to learn before you start.