Vermiculite

Vermiculite is a natural mineral expanded into soft, spongy flakes that soak up water and hold it in reserve. Where perlite is about drainage, vermiculite is about moisture, which is why the two are so often used together to balance a mix.

It is a favourite for seed starting because it keeps the surface evenly damp during germination, and a thin layer sprinkled over newly sown seed holds moisture without blocking light. It also holds on to nutrients and releases them back to the roots instead of letting them leach away with every watering.

Mix it into potting soil for containers that dry out too quickly, or use it on its own for germinating seed and rooting cuttings.