What is perlite?

Perlite is a lightweight granular material that’s white in colour. It looks and feels like little bits of polystyrene but is actually made from expanded volcanic glass, heated to 1000°C until it ‘pops’ (like popcorn) to many times its original size. It’s lightweight, sterile, and easy to handle, and is long-lasting. It’s neither alkaline nor acidic.

Perlite’s expanded nature makes it extremely porous, so it can absorb water, but it also improves drainage, so is ideal to mix into compost to ensure water drains freely. Perlite is particularly useful in plant propagation, including taking cuttings and sowing seeds. Other materials that perform similar functions are vermiculite, grit and sharp sand.