The substratum for epiphyte orchids
The nature of this substatum isn’t very important as its purpose is to support a plant that lives on a tree. It should be as inert as possible, ventilated, and it should retain an amount of water suited to the growing conditions of the plant in its original environment (thus it is important to know the name of the plant).
You can use
- horticultural pine bark, which lasts around 3 years.
- well washed coconut fibre, which will get rid of sea salt (be careful of rot caused by over-watering).
- cork cut up into small pieces (wax-free wine corks).
- or a mixture of one of the above with polystyrene of different sizes, or with a small quantity of perlite or vermiculite (this helps roots to sprout).
Some epiphytes are sold in baskets. They may be repotted to help them grow. Or you may simply place the basket in a suitable pot three quarters full of humidified clay stones.
We could all go out of our minds trying to find a personal mixture – but it is much simpler just to use horticultural pine bark (not that used for embankments) of different particle sizes, depending on the thickness of the roots. A small particle size is suited to thin roots, medium or big sizes to the others. Good stability and drainage can be obtained by putting 2cms. of clay stones or bits of broken pots at the bottom. It you suspect that the bark contains parasites or fungii, pour some hot water over it or boil it a bit to desrtroy these nuisances.
The substratum for terrestrial orchids
It is much safer and simpler to buy the one sold for Cymbidium or boat orchids. You may add polystyrene for ventilation, if necessary.