Potting mix

Potting mix is a blend of materials such as peat or coir, bark, perlite and compost, formulated to stay loose and hold both air and moisture around roots inside a container. It is different from garden soil, which is heavier, compacts quickly in a pot, and often drains so slowly that roots sit in water and rot. Almost every guide to balcony growing starts with the same rule, never fill a container straight from the garden or a bag labeled topsoil.

A good mix stays fluffy after watering, lets excess water drain freely, and still holds enough moisture between waterings that plants are not stressed. Many mixes also include a starter charge of fertilizer, but this feeds plants for only a few weeks, so containers still need regular feeding through the growing season. Mixes formulated for vegetables, succulents or seed starting differ in how much they drain and how much they hold, so matching the mix to the plant improves results.

When buying, look for a mix that feels light and crumbly rather than dense or waterlogged in the bag, and check that it is intended for containers rather than raised beds or lawns. A frequent mistake is packing the mix down firmly when potting up, which squeezes out the air pockets roots need. Topping up settled mix each season, rather than reusing exhausted mix indefinitely, also keeps container plants healthier.