What Types of Soil Do Cacti Need?

Organic Materials

• Cacti require some organic matter in the soil. Compost and garden loam provide trace amounts of nutrients to the cactus, but nutrient-deficient materials like peat moss or finely ground coconut coir also work well. Organic materials retain moisture in the potting mix so it doesn't dry out completely. They also help support the plant, giving the roots material to cling to, which helps hold the plant upright in the pot. Combining equal parts peat or coir with compost or garden loam provides for the organic needs for the cactus.

Drainage Materials

• Cactus naturally grow in sandy, well-drained soils. Coarse builder's sand is included in many commercial cacti soils as well as in homemade soil recipes. Vermiculite can be substituted for the sand, if preferred. This fine-textured, volcanic mineral provides most of the benefits of sand but doesn't sink to the bottom of soil mixes like sand sometimes does. Most cacti thrive in soil mixes that contain one-third sand.

Nutrients

• Most cactus plants can thrive in nutrient-poor soil, but add some nutrients both before and after planting helps keep indoor cacti looking their best. Phosphorus benefits all cactus plants, but especially those that are grown for their flowers. The University of Rhode Island recommends adding 1/2 cup of bonemeal to every 12 quarts of cacti soil to provide for most of the plant's phosphorus needs. Many purchased cactus soils have the bonemeal premixed in. Cacti also need calcium, which is provided by adding ground limestone to soil mixes. Established plants require occasional fertilizing with a soluble cactus fertilizer, which replenishes the nutrients in the soil mix.