Perlite and pumice are both lightweight, mineral-based additives used to improve drainage and aeration in houseplant compost.
The headline difference: perlite is lighter, cheaper, and floats; pumice is heavier, more durable, and stays in place. For most UK houseplant growers, perlite is the more practical choice. Pumice is better when you want long-term aeration that doesn't break down or migrate to the top of the pot.
What Perlite Is
Perlite is a volcanic glass that's been heated to around 900 degrees Celsius until it pops, like popcorn. The result is a brittle, lightweight, white granule full of internal air pockets. It holds a small amount of water on its surface but doesn't absorb moisture into its structure.
Properties that matter for houseplant use:
- Very light. A litre of perlite weighs around 100 grams.
- Floats. It migrates to the top of the compost over time, particularly with top watering.
- Breaks down slowly. After 18 to 24 months it starts crumbling into dust.
- pH neutral.
- Cheap and widely available.
What Pumice Is
Pumice is also a volcanic rock, but unprocessed. It forms naturally when lava cools rapidly and traps gas bubbles inside. The result is a porous, gritty, grey or cream-coloured granule.
Properties that matter:
- Heavier than perlite. A litre weighs around 500 to 700 grams.
- Sinks and stays put. No migration to the surface.
- Doesn't break down. Lasts years without crumbling.
- Holds more water than perlite (about twice as much by volume) thanks to its porous structure.
- More expensive and harder to find in the UK than perlite.
Perlite vs Pumice in a Pot
Both improve drainage and aeration, but they do so differently.
Perlite creates large air pockets but holds very little moisture itself. Mixed at 20 to 30% of a houseplant compost, it stops the mix from compacting and lets excess water drain. The trade-off is that it floats: every time you water from the top, more perlite ends up on the surface. Within a year, you usually see a visible white crust of perlite sitting on top of the compost.
Pumice creates air pockets and holds some moisture inside the granule itself, releasing it slowly to the roots. Mixed at the same ratio, it stays distributed through the rootball. It's the better choice for plants that prefer steady moisture without sogginess: alocasias, anthuriums, ferns, and most calatheas.
Which Plants Benefit Most From Each
Perlite suits:
- Cacti and succulents. Mix 40 to 50% perlite with houseplant compost. Fast-draining, low moisture retention.
- Hoyas and other epiphytes that prefer dry-out cycles.
- Propagation. Pure perlite or a 50/50 perlite-coir mix is one of the best rooting mediums for stem cuttings.
- Anyone on a budget. Perlite is roughly a third of the price of pumice in the UK.
Pumice suits:
- Aroids that want steady moisture: Anthurium, Alocasia, Philodendron, Monstera. Mix 20 to 30% into a peat-free houseplant blend.
- Long-term pot setups. If you don't want to repot for 3 years or more, pumice holds its structure better.
- Bonsai and orchid mixes. Many growers use pumice as the main aeration component alongside bark.
- Anywhere migration is a problem. Top-watered plants on a windowsill where you don't want a visible perlite crust.
Browse our substrate range for our own blended mixes. We use a combination of both perlite and pumice in our aroid blends, depending on the species.
Can You Use Them Together?
Yes, and we often do. A common ratio for high-performance houseplant mixes is 60% peat-free houseplant compost, 20% pumice, 10% perlite, 10% fine bark. The pumice holds moisture and stays put, the perlite adds extra aeration in the short term, and the bark contributes coarse structure for climbing aroids and epiphytes.