Marijuana grows best in a soil-based potting mix that contains perlite. The perlite gives the soil the extra air it needs while the potting mix offers nutrients and structure. The best soil for starting cannabis plants will contain three key ingredients: Perlite - The first ingredient is perlite, which is a type of volcanic glass. It is used to add extra drainage to the soil and aeration, which helps plants grow faster and healthier. Perlite also helps prevent over-watering by draining water away from the roots so that they don’t get too wet. Vermiculite - Vermiculite is another popular component in potting mixes because it holds water well and releases it slowly over time, as needed by your plant. This prevents over-watering problems and keeps your plant from drying out too quickly if you forget to water for a day or two during hot weather when you are away on vacation! Sphagnum Peat Moss - Sphagnum peat moss contains humus, which is decomposed organic matter that goes back thousands of years sometimes! This stuff has been through a lot and still has plenty left to offer your garden... including lots of nutrients!