Vermiculite is a heat-treated, pure clay mineral of natural origin. It is suitable for use in potting mix, for covering seedbeds, for rooting cuttings, and for the winter storage of vegetables and flower bulbs. Vermiculite can absorb up to 500 times its weight in water; it is extremely lightweight, sterile, and weed-free. Vermiculite is suitable for plants that require neutral growing medium. It is also suitable for use in organic farming. Vermiculite should be mixed with soil in a 1:1 ratio. This improves the structure of the growing medium and increases its water-holding capacity.