Most growing media consist of varying proportions of peat moss, vermiculite, and perlite

They also may contain limestone and a wetting agent. Some media are "charged" with nitrogen, phosphorus, potassium, and some micronutrients, as well. A simple homemade medium mixture can be prepared in the following proportions: 1 gallon peat moss, 1 gallon vermiculite, 1 tablespoon superphosphate, and 2 tablespoons ground limestone.