Vermiculite water retaining soil improver.
Vermiculite added to the garden or vermiculite in potting soil increases water and nutrient retention and aerates the soil, resulting in healthier, more robust plants. Perlite may also be found in potting soils, but vermiculite is far superior for water retention. Vermiculite, although it is able to hold less air than perlite, is the correct choice for more plants liking more water.
Vermiculite is the name of a group of hydrated laminar minerals (aluminum-iron magnesium silicates) which look like mica. Horticultural vermiculite is processed with massive heat that expands it into accordion shaped pellets composed of multiple layers of thin plates. It will not rot, deteriorate, or mould and is enduring, odourless, non-toxic and sterile.