Container gardening is an excellent option when gardening space is limited (or when your natural soil isn’t up to snuff), and it’s simple enough to apply organic principles to the effort. However, you need to be aware of certain factors if you want to maximize your success, starting with the growth medium you use.
Plain garden soil or topsoil simply won’t do; although it’s fine when it’s in the ground, its properties make it a poor choice for container gardening. Not only can it get waterlogged and easily compacted, it often contains weed seeds and other foreign matter you can live without.
Your best option is a specific type of growing medium that’s usually called potting mix, though it sometimes goes by other names. You’ll need to look for a medium containing very little, if any, soil at all. True potting mix is formulated specifically for container gardening, tends to be sterile, and always contains materials like vermiculate, sphagnum moss, and perlite. Some brands may also have compost, bark fines, and other organic matter mixed in. The different-sized particles allow water and air to flow through the potting mix easily, so that you’ll get quick draining when too much water is present. Plus, in the case of self-water containers, potting mix allows water to wick upward to the plant’s roots.
So be cautious when purchasing your potting mix, and look carefully at the label. Many commercial potting mixes come pre-soaked in chemical fertilizers, which makes them pretty much useless for organic gardening. If you look hard enough, you can find potting mixes enhanced with natural fertilizers, or you can just opt for plain potting mix. It’s not hard to mix in some compost to enhance the potting mix’s fertility.
Properly cared for, the potting mix in a particular container should last for 5-6 growing seasons. After that, it’s ready to be worked into the compost heap.