There are almost as many recipes for orchid potting mixes, as there are orchid hobbyists. The most commonly available mixes are based on bark; usually fir or redwood. Bark is inexpensive, comes in a variety of sizes and has a rough surface and leaves plenty of air pockets for the free circulation that orchids need. Unfortunately, the bark softens with age (approximately 2 years) and watering and starts to compact, cutting off the air supply and damaging roots. Common additives to help keep the bark from compacting are horticultural grade perlite, hardwood charcoal and peat moss.
Potting an orchid with bark mixes is very simple. The mix should be soaked overnight in water to break the surface tension of the resins, making it easier to wet the bark. Dry bark in a pot will not soak up much water and will dry more quickly. Because of the natural breakdown of the bark by a fungus that consumes nitrogen, orchids in bark need a fertilizer higher in nitrogen. Varying sources recommended a ratio of 30-10-10 or 20-10-10 to be sure that the plant receives enough nitrogen for growth.
The next most popular potting mix ingredient is tree fern fiber. The fibers are very thin, black sticks that are the roots of tropical fern plants. The twiggy nature of the fibers prevents them from packing down tightly and cutting off circulation. The fibers come loose for adding to mixes, in chunks for use in slatted baskets, in plaques and totems for mounting and carved into balls or pot shapes. Watering generally needs to be more frequent, as the water drains away very quickly. Tree fern fiber is popular in areas of high humidity, such as Florida.
Another frequently used component is sphagnum moss. This spongy material comes from peat bogs in a number of species. The moss holds a lot of water and can become packed down if left too long in a pot. Shredded coconut fiber is a popular substitute for sphagnum moss.
Some of the less frequently use potting materials include wine corks, lava rock, gravel, rubber from recycled tires and rock wool.
When you are starting out in the orchid hobby, you should be able to use a packaged orchid mix available at your local garden center for the most popular beginner plants. When you inevitably want to move on to more difficult species, then you should research any specialized needs that your plants many have.
