From our perspective as plants, our most critical need is a potting medium that does not hold excess water around our roots. Our fleshy leaves and stems are designed to store moisture for long periods, making us highly susceptible to root rot. The "best" soil is one that allows water to flow through it almost immediately after watering, leaving the particles only slightly damp. A dense, moisture-retentive soil is a death sentence for us; it suffocates our roots, promotes fungal growth, and leads to a rapid and irreversible decay from the bottom up.
We thrive in an environment that mimics our native, often arid, habitats. This means the soil must be extremely well-aerated. The perfect mix feels gritty and loose, not dense or clay-like. This structure is achieved by combining a small amount of organic matter with a large proportion of inorganic, coarse materials. The inorganic components create permanent air pockets, ensuring our roots have constant access to oxygen and preventing the soil from compacting over time. This loose structure also makes it easy for our roots to grow and expand freely throughout the pot.
The ideal blend for our health consists of two main parts. First, a small amount of organic potting soil, which should be a coarse, well-sifting mix without any fine peat or moisture-retaining crystals. This minimal organic component provides a tiny amount of nutrients and a hint of moisture retention. Second, and most importantly, a large proportion of inorganic gritty materials. We are particularly fond of coarse sand (horticultural, not beach sand), perlite, and pumice. These materials are non-absorbent, provide weight for stability, and are the primary agents that create the fast-draining, aerated environment we crave. A ratio of approximately 40% organic potting soil to 60% inorganic grit is often perfect.
When planted in standard potting soil or a mix that is too organic, we face immediate and severe stress. The soil will stay wet for days, even weeks. Our roots, unable to breathe, will begin to die off. As the root system fails, it cannot transport water and nutrients to the rest of the plant, leading to the ironic situation where a succulent in soggy soil appears to shrivel and wilt—a sign of root death, not underwatering. Furthermore, compacted soil creates a physical barrier, stunting our growth and making it difficult for us to establish a strong, healthy root system to support our above-ground parts.
