Orchid Growing Substrates

older roots. The new roots that are formed in the new potting mix should help the plant to restart.
However, for some plants it cannot be done without a great setback to them, especially the
odontoglossum and miltoniopsis, which can be killed in the process, or severely stunted. The whole
root system was acclimatized to very wet conditions, and is not hardened enough to survive in a drier
potting mix, or even with pathogens, fungus, bacteria around, so it will die. Usually, when a sympodial
plant loses all of its roots, like an odontoglossum, the older rootless bulbs and growths will die, as the
new growth will make roots for itself, can sustain in part the older bulbs, but not completely. When
some of the older bulbs die, they can start to rot, generate acidity, which greatly helps pathogens
entering the new growth, which means a total plant collapse.
- On a medical point, there are some unclear points, even as of today. Maybe we do not have the
required knowledge to understand, but so far several countries charge a premium for Rockwool
disposal, as a toxic waste. , the dusty thorny Rockwool with residues of some years of phytosanitary
chemicals do not seem to be good for the environment. On to two other points, it has been claimed
by some manufacturers that first, Rockwool, unlike asbestos, even if it will target, and successfully
reach the same location in the lungs will ‘dissolve’ in the lungs by the ‘acidity’. On the other side, it is
not dissolved by hydrochloric acid, at least it is only partially dissolved, with a residue. It is hard to
understand where the solid residues from such a magic ‘dissolution’ would end up in the core of the
lungs, if they would be teleported like in Star Trek out of the human body, or encysted, or whatever?
The second point, some years ago Rockwool showed unacceptable levels of arsenic, lead and
mercury. Again, it has been claimed at that time that the strong alkaline reaction of Rockwool
prevented their assimilation and uptake by food crops on Rockwool slabs. However, plants do
generate organic acids at their roots, the feeding solution is acid, and there would be a lot of
microorganisms that can do a lot of funny to some compounds.
Lava rock, aggregate, stones, perlite
Lava Rock Pumice Perlite
- A lot of recipes call for various types of stones, pumice, red lava rock, clay aggregates, seramis, perlite,
gravel. However, depending on their sources, the results can be really different, and their chemistry
makes them non inert. I suspected for years that growers using red Lava rock got some micronutrients
out of it, and apparently it is the case. Some lava rock sources have a very high content of iron,
manganese, eventually even potassium. It depends on the volcano, and even on the particular
eruption. Without entering in a lot of details about geological matters, this kind of stones and
aggregate materials have a wide range of application. However, there are some things that are little
known from the users. First, pumice is one of the best stones available out of the whole series. It has a
grey color, and can be calibrated to a uniform size. Some types can be partially or totally hygroscopic,
retaining easily water, whilst providing good drainage. However, most serious traders of pumice have
to either extract it from permafrost areas, or areas with an extremely cold winter. The reasons lie in
the fact that some sources have been found to be very heavily contaminated by pathogenic
nematodes. Nevertheless, for all those stones, including the processed perlite, the salts concentration
must be assessed, and this needs to be done in two ways. Some pumice as an example floats for the
first few days when dropped in a water bucket. Then, suddenly, after one or two weeks, they will
absorb a lot of water, be saturated and drop at the bottom. If one tests the pumice water extract the
Xavier Garreau de Loubresse
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