Soil Used for Planting Cactuses

Indoors Mix #1

• Because cacti are succulent plants, absorbing and retaining water in the plant itself, they require a very well draining planting medium that does not retain much water for the roots to wick up. Therefore, a sandy based soil is recommended.
  You can easily make soil for cacti if you make sure all ingredients are sterilized to avoid soil-borne diseases. A standard soil mixture for desert plants, from the University of Rhode Island calls for: 1 part coarse builder's sand, 1 part garden soil and 1 part peat moss.

  Add half a cup of bone meal to each twelve quart pail of this mixture. Planting in clay pots is recommended because the clay allows the soil to dry out quickly between watering. Be sure your garden soil does not contain organic materials like manure or wood chips or sawdust. This will cause your cacti to do bursts of growth, which will weaken it and may kill it. Builder's sand is recommended for its sterility. Do not use sand from the beach because it contains a high level of salt. When you are done potting your cactus, put a layer of gravel or pebbles on top of the soil to help stabilize the cacti and keep the moisture level more uniform.

Indoors Mix #2

• A more complicated mixture is found at cactus-guide.com. Equal parts of the following are mixed together for a cacti potting medium: coarse builder's sand, leaf mold, clay soil or garden loam and charcoal. To that, add half as much broken brick and mix in one teaspoon each of slack lime and superphosphate. Leaf mold is used because it is rich in nutrients and absorbs water well. Clay soil will retain water. Builder's sand creates porosity in the soil. Charcoal keeps the soil fresh. Broken brick helps with porosity and absorbs water. Slack lime assists the cacti in taking up nutrients. Cacti prefer a higher pH soil, and the superphosphate will increase the pH in the soil.

Outdoors

• Cacti grown outdoors also needs very well draining soil. If the soil where you want to plant the cacti is humus rich or contains a lot of organic material, you need to build up a planting bed. You can do this by either digging a shallow pit or building a raised garden bed type structure. Add a thick layer of rocks, bricks, broken tiles or a mixture of these to the pit or raised bed. Then cover the rock layer with a loose grain soil, similar the the potting mix for indoor cactus.