There are several good growing media for cannabis, soil for potting being the most popular. Many closet growers like to use Fox Farm’s line of potting soils as they come with many important nutrients already mixed in. (In fact, using this particular brand means that you won’t be having to give your plants any additional nutrients for the first couple of weeks after germination.) The soil is also conditioned to fall within the desirable ph range (between 6 – 6.5ph, or slightly acidic) that plants need.
You can usually find the Fox Farm brand of potting soil at your local hydroponics supply stores. If it is not readily available, the next best option would be to use another quality potting soil like Miracle-Gro. Just make sure that whatever your soil medium choice is, that it has vermiculite mixed into it.
Although this guide is geared toward growing your plants in a soil-based medium, one alternative to using soil is to instead use a substance called rock wool (usually sold under the brand name of Grodan). Rock wool is made from crushing and melting rock, then spinning it into porous sheets or blocks that seeds can then be planted in. Although it can be somewhat pricey, some of the benefits that rock wool provide is that it is ph neutral, retains liquids extremely well, and can be re-used a number of times. Originally intended for use by large-scale hydroponic growers, it has found some acceptance by other growers who stop short of committing to a true hydroponic set-up.
An 8″ clay or ceramic pot works well for indoor closet growing as it can accommodate up to 3 plants effectively, in addition to being very portable. First, cover the bottom of the pot with about an inch of rocks (lava rock, pea-sized gravel or larger, or even broken pottery shards will work fine). This bottom layer of material will help with plant drainage and prevent your plants’ roots from becoming waterlogged.
Next, fill the remainder of the clay pot with your potting soil. Shake the pot lightly to get the potting soil to settle down into it, and stop filling it when it is about an inch from the top. That’s all it takes to prep your growing containers.
Your next step is to consider what type(s) of cannabis seeds you’re going to plant.