Perlite: Optimise Soil Aeration and Drainage
Perlite is one of the most effective additions for improving any substrate. Light, neutral, inert and 100% natural, it solves in a single step the two most common problems of pot growing: lack of aeration and poor drainage. Here is how to use it according to your plants and your needs.
What is perlite?
Perlite is a mineral of volcanic origin (hydrated obsidian) expanded at high temperature. This expansion creates a porous, honeycomb-like structure that gives it three key properties:
- Drainage — excess water runs off freely, with no excessive retention
- Aeration — the pores keep pockets of air around the roots
- Lightness — it lightens heavy potting mixes
Perlite is chemically neutral (pH 7), does not break down and releases no substances into the soil.
The 5 uses of perlite
1. Improve the drainage of universal potting mix
Universal potting mix on its own tends to compact and retain too much water. Add 20-30% perlite to lighten the mix and prevent root rot. Recommended for the vast majority of houseplants.
2. Substrate for cacti and succulents
Cacti and succulents need a very free-draining substrate that dries quickly. Use 40-50% perlite mixed with cactus potting mix to reproduce the conditions of their natural habitat.
3. Seedlings and cuttings
Pure perlite, or a 50/50 mix with potting mix, is ideal for cuttings and seedlings. It holds moisture without suffocating young roots, which encourages quick, healthy rooting. Compatible with willow water as a soak to stimulate rooting.
4. Mix for orchids
Orchids in closed pots benefit from adding 20-30% perlite to the bark substrate to improve root aeration. Their roots need oxygen between waterings.
5. Drainage layer at the bottom of pots
As a replacement for, or addition to, clay pebbles, a 3-4 cm layer of perlite at the bottom of pots without drainage holes prevents water from stagnating.
Recommended proportions by plant
| Plant type | Recommended % perlite |
|---|---|
| Tropical plants (Monstera, Pothos) | 20% |
| Standard houseplants | 20-30% |
| Orchids | 20-30% |
| Cacti and succulents | 40-50% |
| Cuttings and seedlings | 50% or pure |
FAQ: your questions about perlite
Perlite or clay pebbles: what is the difference?
Both improve drainage, but in different ways. Perlite is lighter and mixes straight into the potting mix. Clay pebbles retain more moisture and are generally used as a drainage layer or on the surface. For maximum drainage (cacti, succulents), perlite is more effective. For regulating humidity (tropical plants), clay pebbles are a complementary choice.
Can perlite be reused?
Yes. Rinse it with clean water after use. It does not break down and can be reused indefinitely in new mixes.
Does perlite feed plants?
No, it is inert and provides no nutrients. It improves the structure of the substrate but must be combined with a fertiliser to feed the plants. A Jungle Boost in the pot covers nutrition for 2-3 months.
Can perlite be used outdoors?
Yes, it is very useful for lightening the substrate in balcony planters and improving the drainage of outdoor pots. Particularly recommended for Mediterranean plants in pots (citrus, olive trees), which hate having their feet in water.