Don’t use garden soil in containers, but use a potting mix specially formulated for the plants you grow. Look for potting mixes that are high-quality and meet the standards in either regular or premium. There are special potting mixes for terracotta pots, hanging baskets, orchids, roses, African violets, acid-loving plants, Australian native plants, bulbs and many other types of plants.
Potting mixes are made from composted pine bark with added fertilizers and soil-wetting agents. Some also contain bark, gravel and other products for improved drainage and aeration.
In large containers where plants may grow undisturbed for several years, it is possible to add bagged soil or compost to the potting mix. The larger the container and the plant, the higher the percentage of soil needs to be–you can include a ratio of up to 50:50 potting mix to the soil. The addition of soil reduces slumping in the pot which will be noticed when soil levels appear to drop. Soil added to the potting mix will also make pots heavier and less prone to blowing over in windy or exposed situations.
One traditional gardening tip that you don’t need to follow when using modern potting mixes is adding drainage materials to the base of pots. This is no longer necessary and indeed can adversely affect drainage in the pot and may also provide homes for unwanted pests such as snails and ants.
To avoid potting mix washing through the drainage holes in the base of pots, cover the holes with a layer of mesh or shadecloth.