For many growers, especially those just beginning to develop a collection, choosing the right potting media can be a challenge, there are a number of choices readily available on the market and no shortage of opinions about which is best for a collection. Whenever you are making a change in media, do it slowly. Test how your plant responds to the new mix in your growing area before moving them all over. This is a lesson many growers learn the hard way coming back from a conference or meeting where the virtues of a particular mix are extolled, disappointed only to discover that their growing area is too wet, dry, warm, etc. and their plants begin to fail.
When working to identify the right mix, you first must consider the plants you are growing. Look at the characteristics of your plants’ roots. Plants with thicker roots have generally evolved in habitats where they aren’t sitting with ready access to water. They are likely harvesting it either from passing showers or through atmospheric humidity. Phalaenopsis and Cattleya roots are good examples of this structure. Both plants are primarily epiphytes (growing on trees) and have thick roots designed to hold water in between water events.
Thinner roots generally indicate that plant is used to accessing water in a more conventional way and more readily. The thinner roots are not designed to hold water as long for the plant. Both Phragmipedium and Masdevalia have thinner roots. Phragmipedium naturally grow in seepages and along stream banks. The roots have constant access to water making it so that they don’t need to store as much for the plant. Masdevalia also have constant access to moisture. Naturally growing in the cloud forests of Central and South America, these plants grow in clumps of organic matter that are continually whetted by the clouds and fog lessening the plants need to store water for longer periods of time.
The next factor to consider is the conditions of your growing area. If you are growing with high humidity and a lot of water, mixes that allow for better drainage and air flow will help your plants thrive if it has low humidity, you will want to have a mix that retains water. The image outlines some of the common materials available and the pros and cons of using each. You can use it as a guide as you work to match up a mix for your plants.