You may have heard that thatch in your lawn is made of lawn clippings – not so! In fact, lawn clippings are great for your lawn. They start to compost almost immediately providing a good source of potassium, and they help with moisture retention in dry weather. Ideally, you would want them to be chopped up as fine as possible, but that depends on the type of mower you have and how long your grass has grown since the last mowing. Try to mow often enough that you are cutting only an inch or less off the top of your grass.
For those who may be wondering: what is thatch made of, if not lawn clippings? It is made of dead roots and rhizomes. Thatch builds up, over time, in a layer between the green growing grass and the soil. Heavy thatch can limit the availability of water and nutrients to your grass. The best time to deal with thatch is in the fall. Simply rake your lawn vigorously while raking leaves.