Soil and potting mix
Soil and potting mix is the single biggest factor in keeping cacti and other succulents alive. Most losses in cultivation come not from underwatering but from roots sitting in soil that stays wet — so the goal of a good mix is simple: hold a little moisture, then drain and dry out fast. This guide covers what to use, how to blend it, and how the recipe shifts between different kinds of succulents.
Why drainage matters
Cactus and succulent roots evolved in coarse, mineral ground that drains within seconds and dries within days. In dense, water-retentive potting soil those roots stay damp, lose oxygen, and rot — usually invisibly, until the plant topples or softens. A free-draining, airy mix is your main defence against root rot, far more important than any watering schedule.
The two ingredients: mineral and organic
Almost every good mix is a blend of two things:
- Mineral (inorganic) grit — provides drainage, air pockets and weight. Common choices: pumice, perlite, coarse ("sharp") sand, lava rock (scoria), calcined clay (Turface, seramis, cat-litter marketed as 100% calcined clay), and akadama (popular for bonsai and prized succulents).
- Organic matter — holds a little moisture and nutrients. Common choices: coco coir, a quality peat-free potting compost, or composted fine bark.
A reliable starting point for most cacti and succulents is roughly half mineral, half organic — for example one part pumice or perlite, one part coarse sand or calcined clay, and two parts of a good potting mix. Growers in hot, dry climates or with heavy hands on the watering can lean more mineral (70 % or more).
Adjust the recipe to the plant
| Group | Mix leaning | Notes |
|---|---|---|
| Most cacti, echeverias, aloes, haworthias | ~50 % mineral | The all-round blend above works well |
| Lithops and other mesembs | 80 %+ mineral | Very lean, gritty; almost no organic matter |
| Ariocarpus, Aztekium, other slow "living rock" cacti | 70–90 % mineral | Lean and airy; they resent staying wet |
| Epiphytic cacti (Schlumbergera, Rhipsalis, Epiphyllum) | More organic | Add extra bark/coir; they like a moister, chunkier mix |
| Caudex plants (Adenium, Pachypodium) | ~60 % mineral | Free-draining but with enough body to support fast growth |
Getting the details right
- Particle size — aim for grit around 3–6 mm and sieve out the fine dust, which clogs the air gaps you are trying to create.
- Pot choice — terracotta breathes and dries faster (forgiving for over-waterers); glazed or plastic holds moisture longer (better in very dry climates). Whatever the material, it must have a drainage hole.
- Pot size — pot snugly. An oversized pot holds a large reservoir of damp soil around a small root ball and invites rot.
- Top dressing — a layer of grit on the surface keeps the vulnerable neck of the plant dry, deters fungus gnats, and looks clean.
- pH — slightly acidic to neutral is ideal; most peat-free composts and the ingredients above fall in range without adjustment.
Bagged mixes
Commercial "cactus and succulent" soils are usually too fine and organic to use straight from the bag. They make a fine base — cut them roughly 1:1 with pumice or perlite and they perform far better.