It can become a haven for disease and insects. Over fertilization and over watering of your lawn can cause excessive growth and increase the build up of thatch. It is important to maintain a soil pH of 6.5 to 6.8. Micro-organisms decompose thatch best at this pH. Dethatching should be done every 2 to 3 years. This can be accomplished with a specially designed rake, dethatcher blades added to your lawn mover, or a rented dethatching machine.
Early spring is a good time to dethatch.
Aeration helps prevent soil compaction. Aerating machines remove plugs of soil from the lawn and allow water, air, and plant nutrients into the soil. A good time to aerate is in the spring or the fall. Peanut yes after danger of frost and temp.