Orchid Growing Substrates

placed in the proper position, to allow for proper drainage and water absorption, and usually packed
very firmly. There are still ‘potting sticks’ from that era, which showed how hard it was to push the
fibers around the roots. It was either used alone, or blended with sphagnum, in clay pots. The results
were really good, but with some drawbacks, explained further.
- Asplenium, various fern roots. Those are the complete root systems of many different species of
ferns, including Platycerium and polypodium. The fern is dug up, the roots removed, remaining
discarded, and the roots are washed. It looks like a kind of stringy cotton. In fact, in Vietnam and
China the vernacular name is ‘fern cotton’. It can be used as chunks, loosely packed or to fill up a
complete pot. Many plants grow really well in that fern root, including Paphiopedilum gratrixianum,
insigne, and villosum and also the Indonesian mottled leafed Paphiopedilum too, at least at first. The
plants need to be repotted quite regularly, breaking a lot of roots, so it has to be done at the proper
time, and second in some cases, an infection can set up. The pH is an amazing 4.5, but in the countries
where it is used, they use very alkaline river water, or even alkaline city water, which makes a
coherent blend, so the roots are not kept too acidic. It is very interesting to note that :
o
o
o
Whilst plants are beautiful, they need to be kept really wet and watered very frequently. If
they dry out a little bit, many growths will die, no matter what is attempted.
If trying to repot in another potting mix, many growths will die, usually becoming yellow, then
suddenly brown. Pseudomonas sets up in the rhizome and many parts of the roots and
growths base, and kills the plant. Moving a plant out of this kind of cotton fern roots is
exceedingly difficult, and requires the use of antibiotics.
Blending those fern roots with bark and the resulting mix will surely and shortly kill the plants,
no matter the care given. There are a lot of things not understood about this media, that is
very successful as a stand-alone, but due to its rarity, very few analysis have ever been done,
or will ever be done. It is locally feasible to use it, but not on a commercial or export scale, for
sure.
- Osmunda has some of its own problems, including the growth collapse, though osmunda, when
available, can be successfully mixed with bark, unlike the fern roots mentioned above. However, it is
very hard to use another mix after osmunda has been used. The general theory is that those fern
types potting mixes changes something in the micronutrient composition, and when repotted, some
become suddenly toxic for one reason or another. It can be very spectacular, when seeing some huge
Paphiopedilum henryanum potted in those fern roots being potted in any other mix, and getting
yellow leaves overnight, followed by a yellow plant one or two days later, completely brown and
collapsed.
- We cannot be exhaustive for all the potting mixes existing, but fern LEAF is another funny one. There
is a terrestrial fern in Indonesia whose fronds looks like the leaves of a very big Zamia. These fronds
are harvested, and Paphiopedilum are potted in chopped fronds, still green, with the stems and the
leaflets. It was exceedingly successful, and the grower had the best Paphiopedilum superbiens and
tonsum I have ever seen, visibly potted for some years.
- Tree fern. It is the ‘bark’ if one wants to use this term of some tree fern species, dicksonia, even
cibotium and more genera. Again, there are many species, and many types, not clearly identified. In
Vietnam and China we get a type that is more like osmunda, quite fine, branchy thin straw. In Mexico
and South America, they are using both a big straw and a big hollow straw type. It is very unclear how
Xavier Garreau de Loubresse
22