I don't see why you would get flack over that, as most of your post is quite accurate.
In fact, essentially all epiphytic orchid growing is hydroponic, because the potting medium - no matter what it is - is present almost entirely for mechanical support and water & nutrient storage, but does not provide any significant nutrition by itself. In order to do so, the medium would have to decompose, and once that happens we end up with suffocated roots, so we tend to repot before that happens. Moreover, of the organic ingredients used in orchid potting media, osmunda - the roots of one of several osmunda fern species - is the only one that is known to release release any significant amount of usable plant nutrients (especially nitrogen) as it decomposes.
All that said, I got into hydroponics - in the form of semi-hydroponics - as a way to keep my plants alive back in the days when I traveled a lot on business (I averaged 13 flights a week over one 3.5-year period). By using an inert medium, I didn't have to worry about medium decomposition. I ended up with LECA, specifically the PrimeAgra brand, because of it's particular properties with respect to wicking, absorption/release hysteresis, and airiness.
I this case, there are
many ways to "skin a cat", and considering all of the other cultural variables we have to deal with, there is no single combination that is perfect for everyone.
On the subject of diatomite, I still wonder about the "soluble silica" claims. Silica, SiO
2, is remarkably
insoluble in water (I hold Bachelor of Ceramic Engineering and a MS in Ceramics degrees, and am a Corning Glass alumnus). It only becomes significantly soluble if it's in the form of alkaline earth minerals - those based upon sodium, calcium, potassium, and magnesium silicates, for example. I suppose that what makes up the 10% that is not pure silica.
I tried diatomite as a medium in semi-hydroponics quite some time ago, thanks to the generosity of Joe DiDomenico, but had two significant issues with it:
- The sharp, angular form of the particles allowed it to pack too tightly, setting up the formation of bridging water droplets, which suffocated the roots. I am confident, however, that had I used a very coarse grade, my results would have improved. (I used a size roughly equivalent to that of the LECA.)
- The light color fostered the rapid growth of algae, to the point that it eventually completely choked off the top surface. I was not a regular user of preventive measures (Physan or bleach) back then, so again, things might have turned out better if I had.
Dr. Yin-Tung Wang of Texas A&M published an article in
Orchids magazine showing that diatomite did not fully release the minerals in the solutions it absorbed, so expected mineral buildup to become an issue requiring its periodic replacement. Personally, I suspect that's due to the extremely fine microstructure. Its primary industrial use is, after all, as a filter medium!
Besides,
everything will have some mineral buildup over time, it's simply a matter of the rate, and that is determined by more than just the properties of the material.
Hybrid Mode
