Orchid Composts – Part Two
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Two dried and tested compost mixes are given below, but each can be modified to suit individual orchids. Wherever possible, an alternative to fibrous peat should be sought.
Basic Epiphyte Mix: 3 parts washed bark chips (medium grade), 1 part coarse perlag, 1 part charcoal (horticulture grade), 1 part fibrous peat or coir or broken leaves or chopped sphagnum.
Basic Terrestrial Orchids Mix: 3 parts fibrous peat or coir, 2 parts coarse perlite, 2 parts coarse grit, 1 part charcoal (horticulture grade).
A fairly new medium for orchid growing is made up of water-repellent rockwool mixed with perlite. In effect it provides a substrate very similar to that of the mossy branches of trees in tropical forests, with a surface of springy, wet, air bubbles surrounding the plant roots. A carefully controlled system of watering and feeding is obviously necessary with this medium, a different system from that undertaken with conventional composts. It may not be convenient to use both rockwool and other composts for plants in a mixed collection, but for odontoglossums and their allies, paphiopedilums and many orchids in the pleurothallid alliance it is proving more successful than most other composts. On the commercial scale where it is used is very successful, the provision of water and nutrients to plants grown in this a dissimilar mixtures is usually computer-controlled.
For more information on orchid composts, check out Part One!