Horticultural grade Vermiculite is an ideal addition to finer grade potting mixes. It is lightweight, odourless, chemically inert, non-toxic, incombustible, and rot resistant. Vermiculite is a naturally occurring material that helps aerate and loosen the potting media. It also helps with water retention. It is part of our Fine Base Orchid Mix and can be used with sphagnum to make a light, moisture retentive mix for new plants.