Why Standard Potting Mix Kills Succulents
Succulents evolved in conditions most plants would find hostile: rocky, mineral, fast-draining substrates in arid or semi-arid environments where rain is infrequent, intense when it comes, and followed by prolonged dry periods. In their natural habitat, rain events cause water to flow rapidly through mineral-rich, shallow soil and drain away completely within minutes. Succulent roots are adapted to absorb this brief, intense moisture availability and then tolerate extended dry periods — often weeks or months — between waterings.
Standard potting mix — even quality indoor potting mix — is designed to retain moisture. That's its job. For tropical plants that need consistent moisture availability, peat or coco coir-based mix is beneficial. For succulents, it's fatal. A peat-based mix in a pot retains moisture for 5–14 days in typical indoor conditions. Succulent roots placed in this environment face persistently damp substrate that they cannot tolerate — their anatomy evolved for rapid wetting and rapid drying, not chronic moisture.
The result is root rot. The pathogens responsible — primarily Pythium, Phytophthora, and various Fusarium species — exist in almost all soil environments but become pathogenic only in consistently waterlogged, anaerobic conditions. Standard potting mix in a pot creates these conditions for succulents. Their roots begin to rot, turning brown and mushy, and this damage rapidly spreads upward into the stem. By the time a succulent shows visible above-ground symptoms (soft, mushy stem base, collapsing or translucent lower leaves), the root damage is typically severe. For plants already showing these signs, see our root rot guide.
What Succulent Soil Needs to Do
The functional requirements for good succulent soil are the inverse of what most potting mixes are designed to provide. Understanding each requirement helps you evaluate commercial mixes and build effective DIY alternatives.
Fast drainage: Water poured onto good succulent mix should pass through and emerge from the drainage hole within 5–10 seconds. Not minutes — seconds. The mix should not retain any standing water in the pore spaces between particles. This requires large, non-compressible particles that maintain open channels through which water flows freely.
Minimal moisture retention: After the drainage event, the mix should be essentially dry within 1–2 days. Some surface evaporation and tiny amounts of residual moisture in the organic component of a mixed medium is acceptable, but the bulk of the mix should feel dry to the touch within 48 hours of watering in typical indoor conditions.
Good aeration: Particle sizes large enough to maintain air pockets in the mix at all times — even when wet. The root zone needs oxygen; saturated, compact soil deprives roots of oxygen within hours. Gritty, mineral mixes maintain air pockets even at the height of moisture.
Neutral to slightly acidic pH: Most succulents prefer a pH between 6.0 and 7.0. Commercial cactus mixes are formulated in this range. High-peat mixes are typically too acidic (pH 4–5) without lime addition.
Low organic content: High organic matter (peat, compost, worm castings) retains moisture and can compact over time. Succulent mixes should be predominantly mineral with limited organic component. For succulents growing in nearly pure perlite or grit, supplementary feeding is needed to provide nutrients the mineral mix can't supply.
Commercial Cactus Mixes: What to Look For
Many garden centres and home improvement stores stock dedicated cactus and succulent mixes, and these are a valid starting point. However, an important caveat applies to almost every commercial cactus mix available: they are still not dry enough on their own for most succulents in pot culture. Commercial cactus mixes are significantly better than standard potting mix, but they were formulated with some moisture retention to prevent the mix from becoming completely hydrophobic between infrequent waterings. In a pot, this retained moisture is more of a problem than it is in a commercial nursery setting.
When evaluating a commercial cactus or succulent mix, look for: visible grit or coarse particles in the mix (good sign of fast drainage), low peat content (high peat = slower drying), perlite already incorporated (look for the white particles), and a dry, lightweight feel that doesn't clump when squeezed. Avoid mixes that feel heavy and damp out of the bag, clump together when compressed, or are entirely fine-particled without visible grit.
The standard improvement: take any commercial cactus mix and add 50% perlite by volume. Mix thoroughly. This is the single most reliable and cost-effective improvement and produces a mix that performs well for the vast majority of succulents and cacti. After mixing, do the drainage test: water a handful in your hand and squeeze — water should run through immediately rather than being retained.
The Best DIY Succulent Soil Recipes
Making your own succulent mix from components is cost-effective for anyone with a collection of more than a few plants, and produces results that are reliably superior to commercial options used straight from the bag. These recipes use widely available materials.
Recipe 1: The Standard Reliable Mix
50% commercial cactus/succulent mix + 50% perlite
This is the simplest, most accessible recipe and performs excellently for virtually all common succulents (echeveria, sedum, sempervivum, aloe, jade plant) and most cacti. The cactus mix provides the small amount of organic material and nutrients that succulents need, while the perlite dramatically improves drainage and reduces moisture retention to appropriate levels. Total cost per batch is approximately £5–8 for enough mix to repot 10–15 small succulents. Both ingredients are available at most garden centres.
Recipe 2: Pure Mineral Mix
50% coarse horticultural grit/gravel (2–4mm) + 25% perlite + 25% coarse sand
This all-mineral mix has virtually zero moisture retention — it drains as fast as water can flow through it and is dry within hours of watering. It suits the most drought-tolerant succulents and all cacti that have high intolerance for any moisture. Because it contains no nutrients, plants growing in this mix need regular liquid feeding during the growing season (a diluted balanced fertilizer at quarter strength, monthly). Well-suited to lithops, very drought-hardy cacti, and any succulent that has repeatedly suffered root rot in organic-containing mixes.
Recipe 3: The Advanced Balanced Mix
40% coco coir + 40% perlite + 20% coarse horticultural sand
This recipe uses coco coir as the organic base (preferable to peat for sustainability), with a high perlite proportion for drainage, and coarse sand for additional drainage and weight that prevents the mix from becoming too light and unstable. The coco coir component retains just enough moisture for the plant to access after watering, while the perlite and sand ensure it dries to near-completely within 1–2 days. This balanced approach suits echeveria, haworthia, aloe, and most rosette-forming succulents that like slightly more nutrition than pure mineral mixes provide.
Pure Perlite
100% perlite is a viable growing medium for many succulents, particularly for propagation and for very drought-hardy species. Perlite provides anchorage and drainage but zero nutrition — plants grown in pure perlite must be fed regularly with liquid fertilizer to provide all their nutrients. The advantage is complete drainage with no risk of moisture retention. Propagating succulent leaves and cuttings in pure perlite reduces rot risk during the vulnerable propagation period. Not recommended for long-term growing of most succulents without consistent fertilization.
Perlite: The Single Best Succulent Amendment
If there is one material that makes more difference to succulent cultivation than any other, it is perlite. White expanded volcanic glass with a porous structure, perlite is entirely inorganic, does not compress or compact over time, does not retain moisture, and creates stable permanent air pockets in any growing medium it's mixed into. It's lightweight — a 10L bag of perlite weighs approximately 1–1.5kg, making it easy to handle and mix — and costs approximately £4–6 for 10 litres, enough to improve dozens of small to medium pots.
Unlike sand, which can compact between perlite particles and reduce drainage over time, perlite maintains its open structure indefinitely. Unlike vermiculite, which retains some moisture, perlite is essentially non-absorbent. Unlike bark, which breaks down and compresses over 1–2 years, perlite remains physically unchanged.
The single most useful instruction for anyone growing succulents: buy a bag of perlite and add it to whatever commercial mix you're using. At 50% by volume, it transforms any cactus mix into a fast-draining succulent medium. This one action prevents a majority of succulent root rot cases that arise from inappropriate moisture retention in commercial mixes used straight from the bag.
Containers and Drainage
Even the best soil mix cannot compensate for a pot without drainage. For succulents, drainage holes are even more critical than for other houseplants — the goal is for every drop of water to exit the pot within a short time of watering. A pot without drainage traps water that has nowhere to go, keeping the bottom layer of soil perpetually saturated regardless of how fast-draining the mix is.
Terracotta is the strongly preferred pot material for succulents. The porous clay walls allow moisture to evaporate from the full pot surface — all sides, not just through the drainage hole and soil surface — significantly accelerating the drying process. A succulent in a terracotta pot dries approximately twice as fast as the same plant in a plastic or glazed ceramic pot of the same size. This faster drying is a substantial advantage for drought-adapted plants that need their roots to experience true dry periods.
Plastic pots are acceptable with a fast-draining mix, but they retain moisture longer. If using plastic, reduce watering frequency accordingly and consider a slightly more mineral mix than the 50/50 recipe. Glazed ceramic pots are the least suitable — they retain moisture like plastic but are often heavier and less breathable. Avoid glass containers or decorative pots without drainage holes entirely for succulents.
Pot size also matters. Succulents in pots that are excessively large for their root ball have the same problem as any other over-potted plant — the excess soil volume around the small root ball stays wet for extended periods. Keep succulent pots close to the root ball size: 1–2cm wider than the root ball is appropriate. The small pot size also dries faster, which is exactly what succulents need.
Repotting Succulents
Succulents are best repotted in spring, when they're entering the active growing season. The repotting process for succulents has a few specific differences from repotting other houseplants that reduce stress and rot risk.
First, do not water the day before repotting as you would for tropical plants. For succulents, repotting into dry mix is preferable — the roots are in a drier state and less susceptible to damage, and starting in dry mix reduces the immediate rot risk. Allow the unpotted plant to sit with bare roots in the air for 30–60 minutes before planting in new mix. This brief air-drying allows any minor root damage from handling to begin callusing over, reducing the entry point for pathogens.
After repotting, do not water for 1 full week. The succulent has sufficient reserves to sustain itself for this period, and waiting allows any damaged root surfaces to callus before wet conditions could introduce infection. After the first week, water normally — drench thoroughly, then allow to dry completely before the next watering.
For guidance on how frequently to water succulents and how to read watering signals, see our complete watering guide and our watering frequency guide at how often to water houseplants. For broader soil guidance covering all plant types, see our best soil for houseplants guide.
Frequently Asked Questions
Getting succulent soil right is the most impactful single change most succulent growers can make. The 50/50 cactus mix + perlite formula is reliable, affordable, and works for nearly every succulent species. Pair it with terracotta pots, drainage holes, and careful watering, and root rot becomes rare rather than routine. Further reading: General Soil Guide, Repotting Guide, Watering Guide, and Root Rot Guide.