Potting mixes are one of the most important parts of your growing success. Today’s potting mixes are mostly made up of peat moss, vermiculite and perlite. It’s important to understand why potting mixes are used at all. Potting mixes are only used a a reservoir for your water and micro nutrients. Plants could ultimately grow in just water if you fed them properly. This is why having light and airy soil is so important for good root production – it allows excess water to drain while retaining the nutrients needed.