Given this diversity, it is hard to keep track of what is best for your orchids. In fact, there is probably no "right" answer for everyone. Potting mixes should be designed according to a plant's specific needs AND its growing conditions. Experimenation will surely be necessary.
Regardless, I thought that it might be useful to list the potting mixes of some of the world's top Paph growers. These can serve as starting points for your own mix experiments. As much information about the mixes is provided as possible to help tailor them to your needs.
The Orchid Zone is world renown for growing high quality Paph species, but is especially famous for Mr. Root's complex hybrids. The mix he uses promotes free drainage and oxygen availability to the roots. His mix consists of:
Equal parts bark and lava-rock.
Ms. Congleton uses a much more typical Paph mix, although she also specializes in complex Paph hybrids. Her mix contains the following:
- 8 parts fine bark
- 2 parts #3 perilite
- 1 part charcoal
The Wellensteins have written a considerable amount of information regarding their research with Coconut Husk Chips as an alternative to bark. I recommend that you read their entire article on the subject.
They have published differing mixes for different plants. For paph seedlings, they recommend the following:
3 parts small coconut husk chips, 2 parts #4 sponge rock, 1 part extra-coarse vermiculite, 1/2 part #2 diatomite, 1/3 part horticultural perilite.
For adult paphs:
6 Parts medium Coconut Husk Chips, 3 parts #4 sponge rock, 1 part #2 charcoal, and #3 diatomite is added to suit the particular situation.
Hadley Cash is famous for his complex paph hybrids, but he also grows a surprising number of paph species.
Like the Wellensteins, Mr. Cash uses a mix based on Coconut Husk Chips (CHC) for his paphs. He reports that the CHC lasts up to 3 times as long as bark, allowing him to repot his orchids every 2.5 to 3 years.
His mix is:
5 Parts Coconut Husk Chips (medium, but small for seedlings)
4 Parts Aliflor (expanded clay pellets)
1 Part Charcoal (fine, but extra-fine for seedlings)
Mr. Cash uses the same ratios and same materials regardless of the plant or plant size that he is potting. However, he does use smaller CHC, aliflor, and charcoal sizes for smaller plants and seedlings.