Iris wrote: "In the size particles we use in orchid media, the charcoal holds onto the
excess salts for two years, after which it reaches its capacity & the salts
are released into the medium. That is one reason to repot your orchids every
two years."
Boy, I would like to see the scientific studies behind that claim. Sounds like
a myth to me. I don't expect you, Iris, to produce a study, as I realize you
are only passing along what you have heard. Regular horticultural charcoal
should not hold on to salts any more then most other things we use in our
mixes. As already been explained recently by a number of people about salt
diatomite, the same should hold true for horticultural charcoal. If you flush
your medium, have good water, and don't go overboard with your fertilizer, salt
shouldn't be a big concern.
Whenever someone is selling you the new miracle to orchid growing, like the
lavish advertising of Australian Gold, you should be skeptical. As someone has
already noted diatomite has been sold in the past before as the perfect media
though not with the advertising that Australian Gold. A number of years ago I
tried a sample bag from a company called Sundine Enterprises. They sold
diatomite under the name Isolite. The results were OK, but not any different
then any other media. I am weary of just using one type of media for growing
orchids as you get only the positive and negative aspects of that media. I
prefer a mixed type of media in both composition, shape of particles, and size
(relative to a minimum size). Trying to negate or evenly distribute any
negative aspects of one medium. I think the first flush of new roots and growth
after repotting will happen with just about any medium you chose to use. I
think that flush of roots and growth is mainly timing and maybe orchids
responding to the disturbance of repotting. The real test of a medium or mix is
after some time. As many people have already said there is no panacea media.
The real panacea is to optimize your culture as close to the environment as the
orchid grow in nature.
As to why catch roots exists, maybe they are landing areas for small insect
eating birds. Maybe the ants cause some sort of chemical activation causing an
orchid to produce catch roots and man sometimes activates this in cultivation.
While the orchid may get benefits from having ants nest in them, I am sure
there is also a need to keep the ants in check. Just pure speculation on my
part, do not expect me to produce a study to back this up.
Mark Sullivan
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