An alternative to RO water or rain water?

[Roberta]

For testing, use something that is sensitive to much of anything in the water... like Pleurothallids. They don't care about "ideal fertilizing" ... or much of any fertilizing, but tend to slowly decline with hard water. (My success rate for them improved greatly when I switched to RO water for them)

[DavTom]

Originally Posted by Roberta

For testing, use something that is sensitive to much of anything in the water... like Pleurothallids. They don't care about "ideal fertilizing" ... or much of any fertilizing, but tend to slowly decline with hard water. (My success rate for them improved greatly when I switched to RO water for them)

Many thanks Roberta, much appreciated.
There seems to be a ton of different species. Any of them you specifically owned?

[Roberta]

Originally Posted by DavTom

Many thanks Roberta, much appreciated.
There seems to be a ton of different species. Any of them you specifically owned?

Lots of them... my patio is where I grow most of the sensitive ones. (Take a look a the "growing area" page of my website) I have definitely seen an improvement in survival rate of Pleurothallis species, Dracula, Masdevallia, also Sophronitis (which have been reclassified as Cattleya but still, they have very different needs) Catts, Cymbidiums, Vandas, Paphs, hybrid Phalaenopsis totally don't care what they get - they get tap water ("liquid rocks") This is just at the genus level... And to draw any conclusions, test needs to run for a year or more. Orchids don't do anything fast.,

Note also that fertilizer is the least important cultural factor... get light, temperature, media, watering, air movement right then you can look at effect of different fertilizer approaches.

[DavTom]

Originally Posted by Roberta

Lots of them... my patio is where I grow most of the sensitive ones. (Take a look a the "growing area" page of my website) I have definitely seen an improvement in survival rate of Pleurothallis species, Dracula, Masdevallia, also Sophronitis (which have been reclassified as Cattleya but still, they have very different needs) Catts, Cymbidiums, Vandas, Paphs, hybrid Phalaenopsis totally don't care what they get - they get tap water ("liquid rocks") This is just at the genus level... And to draw any conclusions, test needs to run for a year or more. Orchids don't do anything fast.,

Note also that fertilizer is the least important cultural factor... get light, temperature, media, watering, air movement right then you can look at effect of different fertilizer approaches.

Wow!!! Congratulations for your amazing collection!
I did a bit of research and all the types you mentioned seem to be cool growers. This seems a no go for me as I live in The Netherlands. It is too warm in my house (Winter: min 18 degrees and max 20 degrees; Summer: min 20 degrees and max 30+ degrees; outdoor it is too cold except in mid summer in which both min and max should be OK.

Any other species that would fit my temp constraints?
Preferably without winter rest, so that I can try to boost a bit the growth in my little growing tent (actually it is a mini stealth growing cupboard).

Thanks again.

Cheers,
Dav

[Roberta]

You're right, many of those "sensitive" orchids are relatively cool-growers. From cloud-forest areas. I have a small greenhouse, which also gets RO water since while everything in there may not need it, all benefit and there's not enough room to treat anything differently. Phragmipediums tend to do better with pure water (and most do grow warm). (Paphs totally don't care, some even do better with the "liquid rocks", the ones that grow on limestone cliffs) So Phragmipedium may be a genus with which you could experiment. Or many of the leafless orchids (like Microcoelia or Chiloschista) are warm-growers (also liking lots of humidity)

[DavTom]

Originally Posted by Roberta

You're right, many of those "sensitive" orchids are relatively cool-growers. From cloud-forest areas. I have a small greenhouse, which also gets RO water since while everything in there may not need it, all benefit and there's not enough room to treat anything differently. Phragmipediums tend to do better with pure water (and most do grow warm). (Paphs totally don't care, some even do better with the "liquid rocks", the ones that grow on limestone cliffs) So Phragmipedium may be a genus with which you could experiment. Or many of the leafless orchids (like Microcoelia or Chiloschista) are warm-growers (also liking lots of humidity)

OK! I will:
- buy two identical Phragmipediums. Sorry to still bother, but do you have one to recommend? Maybe one that is leaning more towards a warm growing?
- I will use for both the same light (as much as they can tolerate), humidity, air circulation, semi-hydro conditions. I agree with you that this is more important than fertilization
- One will be fertlized with RO water and rain mix
- The other one with my tap water and the "recipe" I posted in this thread. I will also balance Ca, Mg, K, and micronutrients for both in order to minimize any difference

By the way, I am reinventing the wheel here....the idea to use ammonium to compensate for hard/alkaline water is well known already. For instance, see this article from St. Augustine So, there nothing really new in my post...

https://staugorchidsociety.org/PDF/W...ySueBottom.pdf

Anyway, I think it is still worth to go on with the experiment...

Cheers,
Dav

[Ray]

Without thinking about the chemistry, this discussion has not apparently addressed the fact that rain/distiller/RO water's primary benefit is the lack of dissolved solids. Adding stuff to mineral-laden water only adds more and will not make it comparable.

[DavTom]

Originally Posted by Ray

Without thinking about the chemistry, this discussion has not apparently addressed the fact that rain/distiller/RO water's primary benefit is the lack of dissolved solids. Adding stuff to mineral-laden water only adds more and will not make it comparable.

This is indeed the essence of it Ray, but I think that I have already addressed it (at least implicitly) when I stated several times that we all know that RO water or rain water is the best way to go - no discussion about that.

Why? And now I get more explicit instead,...because it kills two birds with one stone:
1) Ideal PH
AND
2) Low content of salts

Now, if you were forced to chose only one of the two, which one would you chose? I would ALWAYS go for the ideal PH, because it is the PH that greatly effects the solubility and availability of nutrients (in particular most of the micro-nutrients) to the plants.

If the PH is wrong and you do nothing about it, it affects the plant 24/7.

If you have a higher than ideal content of salts, the main drawback (though not the only one - I will get to that later) is the risk of salts build-up. But it is very easy to get rid of it: water/flush your pot regularly! In addition, the semi-hydro method that you invented is probably the most resilient set-up against salts build-up. That is why I will do the experiment in semi-hydro.

However, it goes without saying that even without salts build-up, it is better to have low salts watering than high salts watering. Why? Because this is what orchids get in nature and have evolved over millions of years to adapt to that (obvious statement, but good to remind that) But how much better? The experiment will try to assess that!. For sure there is (actually MUST be) a difference, but maybe it is negligible. Having the PH wrong instead, makes a difference for sure., at least in the longer term.

(By the way, at a very rough guess, I have estimated that with my hard tap water and dedicated fertilizer cocktail for hard water I will get twice as much salts with respect to RO water method. Therefore, I am very confident that weekly watering/flushing - even more so if in semi-hydro, is more than enough to avoid any dangerous salts build-up.)

In conclusion, I share your point with the exception that I believe that the primary benefit (to use your words) comes from the right PH and not from the low salts of the watering. On condition, of course, to be aware of the risks of salts build up and that flashing is required a bit more than with low salts watering...

I hope it helps explain the way I (humbly) see all this...

Anyway, this is a topic that fascinates me...so sorry if I am too verbose...

Ah...one more thing . It is very easy to instinctively believe that hard water (i.e., high content of salts) is the biggest problem. Why? Because in 99% of the cases, hard tap water is also very high in PH! The two go hand-in-hand! On top of that, almost every human on Earth has seen the residual salts of evaporated hard water - it is very tangible, and an easy reaction to that is "I need to purify it, I need to clean it - Yes, RO water; I want RO water" - I also went through all this!; the same cannot be said about the PH - only a fraction of people measure PH because for the non experts it is tedious, needs calibration, needs proper storage!, probe replacement over time, does produce contradictory results if not well calibrated, etc....well it needs extra work! So...the PH story remains much more in the dark, it is much less tangible - you do not see it with your own eyes - and people point consequently the finger to the salts content...And funny enough 99% of the times they still get it right because tap water with high salts content (i.e., hard water) has also an high PH in 99% of the cases....

Cheers,
Dav

[Roberta]

You are chasing an effect that will be hard to see even under the best of circumstances, since orchids grow and thrive with very little of any fertilizer. So even a sub-optimum level due to pH (based on the pH in the medium, not what you put it, which confounds any effect even more) is still not zero... Since most orchids can go months or even years with no fertilizer at all and still grow quite well (maybe not as well as if they had a bit, perhaps), how long do you plan to run this "experiment"?

[DavTom]

Originally Posted by Roberta

You are chasing an effect that will be hard to see even under the best of circumstances, since orchids grow and thrive with very little of any fertilizer. So even a sub-optimum level due to pH (based on the pH in the medium, not what you put it, which confounds any effect even more) is still not zero... Since most orchids can go months or even years with no fertilizer at all and still grow quite well (maybe not as well as if they had a bit, perhaps), how long do you plan to run this "experiment"?

As long as needed...Actually you made me think that probably the best set-up is to have three, not two, identical orchids in the very same conditions apart from the chemistry of the water: 1 with my hard alkaline tap water with normal fertilyser that does not reduce PH; 2 with my hard alkaline tap water and fertilyzer that reduces the ph to 6 (by the way, with the semi hydro method it is very easy to esrimate the real PH of the roots by measuring the PH of the reservoir); 3 with RO water and rainmix.

On the long term I would expect some evident difference between 1 and 3. The biggest question mark is how 2 will perform against 1 and against 3. My educated guess is that 2 will perform closer to 3 than to 1. My hope is that 2 will perform so close to 3 that there is no significant difference between the two.

Cheers,
Dav