While caring for a cactus is relatively easy, potting one can be a little more complicated. The makeup of the soil is key, since cacti have specific density and nutritional requirements. The perfect potting soil should wet easily, drain well and contain some organic material for proper nutrition and adequate air. The soil should not be so rich that it holds water for long periods, though, because this will inevitably rot the roots. It is easy to make your own cactus soil at home with ingredients you can get at your local garden center.
Obtain good-quality top soil, peat moss and crushed pumice or vermiculite from your local garden supply store or nursery.
Make a mixture of 20 percent top soil, 10 percent peat moss and 70 percent pumice or vermiculite in the mixing container. Combine thoroughly to form the foundation for the cactus soil. Moisten the soil so that it is damp.
Sterilize the soil. Place the mixture in a plastic bag, insert a cooking thermometer into the soil through the bag, place the bag on an oven tray, and heat the soil in the oven until it reaches an internal temperature of 165 degrees.
Add 1/2 cup of bone meal for every 12 quarts of soil mix to ensure a proper pH balance and a good-quality, general-use, timed-release fertilizer such as Osmocote. Mix these two ingredients into the soil thoroughly.