This bark has been selected for the use with Orchid Plants, the 6-12mm size is a good grade, to repot Phalaenopsis, Oncidium Type orchids, contains very little dust. Can be used straight from the bag. But we recommend to soak the bark overnight before use in your favourite fertilizer this will then give you plant roots a head start. Fertilizers recommend by Orchid Accessories Orchid Focus Grow and Bloom (Liquid Feed) Dyna-Gro Orchid Pro, or (Grow and Bloom) (Liquid Feed) Rain Mix (Powdered Feed)