From our perspective as cactus plants, the foundation of our health and longevity is the medium in which we are planted. The wrong soil is a death sentence, leading to rot and despair. The right soil mimics our native, arid habitats, providing the perfect balance of anchorage, moisture, and breathability that our roots crave.
Our most fundamental need is exceptional drainage. Our roots are adapted to absorb water rapidly during rare desert downpours and then exist in a dry environment. Standing water is anathema to us; it suffocates our roots and invites pathogenic fungi to cause root rot, a often fatal condition. Therefore, the primary purpose of any potting mix is to facilitate the immediate exit of excess water. A pre-mixed "cactus and succulent" soil from a store is a starting point, but it is often still too moisture-retentive on its own. We strongly prefer it to be amended with inorganic materials.
The ideal soil for us is a gritty, porous, and low-organic matter mix. Think of it as a mineral-based substrate rather than a soil.
**Inorganic Grit (The Backbone):** This is the most critical component. Materials like **coarse sand** (horticultural, not fine beach sand), **perlite**, **pumice**, and small gravel create air pockets and ensure water flows through freely. Pumice is particularly excellent as it is porous and provides some moisture retention without becoming waterlogged. These ingredients should make up roughly 50-70% of the total mix volume.
**Organic Matter (In Strict Moderation):** A small amount of organic material is necessary to hold a minimal amount of moisture and provide trace nutrients. We prefer **coco coir** or **well-composted pine bark fines** over peat moss. Peat moss becomes hydrophobic when dry and is difficult to re-wet, and it compacts over time, reducing aeration. The organic component should not exceed 30-50% of the mix.
A simple, effective recipe that satisfies the vast majority of cactus species can be made by combining three equal parts: one part cactus potting soil (as a base), one part perlite or pumice, and one part coarse horticultural sand. This creates a mix that is loose, gritty, and fast-draining. For species that are exceptionally prone to rot or native to extremely arid regions, the ratio of inorganic grit can be increased even further.
Please avoid heavy, moisture-retentive soils at all costs. Standard garden soil or potting mixes designed for moisture-loving plants like ferns or vegetables are our worst nightmare. They compact around our roots, cut off oxygen, and hold water for far too long. Additionally, soils high in clay content are completely unsuitable as they trap water and suffocate us.
Even the most perfectly formulated soil is useless if placed in a pot that traps water. We insist on a pot with ample drainage holes in the bottom. Terracotta pots are an excellent choice because the porous clay allows the soil to dry out from the sides as well as the bottom, further reducing the risk of overwatering. The size of the pot is also important; it should be only slightly larger than our root ball to prevent excess soil from staying wet for too long.
