Getting the compost right is the single most important thing you can do for your cacti and succulents. These plants evolved in environments where water is scarce and the ground dries out fast — they need a growing medium that behaves the same way. In standard houseplant compost, which holds moisture for days or even weeks, cacti and succulents are sitting targets for root rot.
What Cacti and Succulents Need From Their Compost
Cactus and succulent roots are built to drink quickly during brief wet periods, then sit dry for a long stretch afterwards. Their compost needs to do three things well: drain fast (excess water should leave within seconds of watering), allow air to reach the roots even when moist, and dry out within a day or two rather than staying damp. Standard houseplant compost does none of this well enough, and is the number one cause of root rot in these plants when grown in UK homes.
Choosing the Right Mix
The simplest and most reliable option is to use a compost formulated specifically for these plants. Our Desert Mix is blended for cacti, succulents, and other drought-loving plants that need sharp drainage and fast dry-out times. Our Simply Cacti and Succulent Mix is a simpler and more affordable option.
Both mixes feel almost sandy and coarse in hand, which is exactly what you want. If a cactus compost feels dense, dark, and moisture-retentive, it's not doing its job.
If you prefer to mix your own, combine standard compost with coarse perlite or horticultural grit in a ratio of roughly fifty to sixty percent compost and forty to fifty percent inorganic material. Perlite is lightweight, doesn't decompose, and drains freely. Horticultural grit is heavier but works just as well.
Pot Choice Matters as Much as Compost
Compost and pot work as a pair. Terracotta is the best option for cacti and succulents as it's porous, so moisture evaporates through the walls and the compost dries out between waterings. Plastic and glazed ceramic hold moisture for significantly longer.
Every pot must have drainage holes. Standing water, even briefly, dramatically increases the risk of rot.
Pot size matters too. Cacti and succulents do best in pots only slightly larger than the root ball — one to two centimetres wider than the plant base. An oversized pot holds a large volume of compost that stays wet around a small root system, which is a fast route to trouble.
Topping With Grit
A thin layer of fine grit, coarse sand, or small pebbles on the compost surface is a small step that makes a real difference. It keeps the base of the plant away from damp compost, improves surface drainage, deters fungus gnats, and looks good. It's optional, but well worth doing for rot-prone species or plants in lower light where compost dries more slowly.
Refreshing Your Compost
Even the best cactus mix breaks down over time as the organic component decomposes. Repotting into fresh compost every two to three years keeps drainage performing as it should. Spring is usually the best time to repot, when plants are entering active growth and can re-establish quickly.