Crushed oyster shell top dressing Paphs

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Ray

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Ray, why is 'pour through' better than part submerging the pot in RO water, waiting, then removing the pot and taking the measurements? Surely allowing plenty of time for the potting mix to equilibrate with the water better reflects what's going on in the mix?
"Pour through" is a standard commercial nursery method, so that gives it some credibility. Plus, and this is just speculation on my part, I think the volume difference might play a role what are we talking about? 50 ml versus 500 or 1000?
 

Ray

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I was thinking more about that, @Ozpaph, and while pH is a measure of the relative ratios of + & - charges, which ought to be the same no matter the volume, maybe in a larger volume makes measurement more difficult, because of fewer ions overall, per unit volume???
 
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Ray

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That's possible, I suppose, but how will you know? The microbes are aerobic though, so I wonder if being submerged "shuts them down" for a bit.

This article compares 3 different tests, and only one of them uses a "dilution factor" as high as 2:1. Unfortunately, they only give results for EC, not pH.
 

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Plants from alkaline habitats can grow equally well with ph in the acid or alkaline range as long as the Ca is at least 4 times higher than the Mg
How you do that is up to you. I use calcium carbonate and maybe some gypsum.
 

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Ray

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Plants from alkaline habitats can grow equally well with ph in the acid or alkaline range as long as the Ca is at least 4 times higher than the Mg
Is it wise to equate the performance of ferns that tend to be invasive (i.e., can grow anywhere) to orchids that are niche plants? I'm not saying it's not applicable, but the broad statement seems risky.
 

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I grow brachies decently and most say they need some sort of lime additive to the mix. I never do. I make sure to use calcium nitrate
 

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Is it wise to equate the performance of ferns that tend to be invasive (i.e., can grow anywhere) to orchids that are niche plants? I'm not saying it's not applicable, but the broad statement seems risky.
Those ferns are not invasive and grow anywhere. They are limited in their habitat to carbonate rock fissures though they obviousy grow colder than paphs.. The above findings will apply to all plants evolved to grow on limestone. (or limestone soils) They pretty much grow like many paphs do....
 
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I grow brachies decently and most say they need some sort of lime additive to the mix. I never do. I make sure to use calcium nitrate
It doesn't seem to matter that much but if you don't want to give N to your plants at a particular time, it's easier to have some solid Cal Carbonate in the mix to check acidity. There was a trial with orchids in 50 to 75% shells (canunda - a soft fossil type shell) and they grew fine. You can use a lot or you can use a little. Nothing will change in the pot until The mix produces acidity when it will be neutralized. I use Cal nitrate occasionally as well - mainly towards the end of the season when light levels are low. Of course your water quality comes into the picture as well.
 

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that's interesting - how much and how often?
I would say approximately every 4th watering.I fertilize every watering and most of the time I use miracle gro 24-8-16 which is urea based. I used to use plant prod 25-10-10 which was urea based too and I loved it. Unfortunately they discounted it!
that's interesting - how much and how often?
 

papheteer

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It doesn't seem to matter that much but if you don't want to give N to your plants at a particular time, it's easier to have some solid Cal Carbonate in the mix to check acidity. There was a trial with orchids in 50 to 75% shells (canunda - a soft fossil type shell) and they grew fine. You can use a lot or you can use a little. Nothing will change in the pot until The mix produces acidity when it will be neutralized. I use Cal nitrate occasionally as well - mainly towards the end of the season when light levels are low. Of course your water quality comes into the picture as well.
thank you!I think I will try to add some limestone to one pot as an experiment.
 

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It doesn't seem to matter that much but if you don't want to give N to your plants at a particular time, it's easier to have some solid Cal Carbonate in the mix to check acidity. There was a trial with orchids in 50 to 75% shells (canunda - a soft fossil type shell) and they grew fine. You can use a lot or you can use a little. Nothing will change in the pot until The mix produces acidity when it will be neutralized. I use Cal nitrate occasionally as well - mainly towards the end of the season when light levels are low. Of course your water quality comes into the picture as well.
I found this on Amazon.

Would this work? Does it need to be washed before use? Worried about salt content.
 

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If you can find calcined oyster shell (that product might be), it will be better, as the firing produces micro cracks that increases the surface area.

I really don’t see a problem using calcium nitrate. Plants that are not actively growing don’t need to absorb calcium. Plants that are actively growing need more nitrogen than calcium.
 

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Those ferns are not invasive and grow anywhere. They are limited in their habitat to carbonate rock fissures though they obviousy grow colder than paphs.. The above findings will apply to all plants evolved to grow on limestone. (or limestone soils) They pretty much grow like many paphs do....
Thanks!
 

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I really don’t see a problem using calcium nitrate.
Remember Xavier used to suggest that he could not get the deep green that he was after with nitrate only feeding? From what I have seen over the years I would say that I tend to agree. This bloke... enkoshi1.html grew beautiful clean brachys with great coloured leaves using Cal nitrate in rock wool but he also used fish emulsion.
 

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I was referring to calcium nitrate as a source of Ca, not as the only fertilizer (although the orchids at the Huntington Botanical Gardens are grown that way).

I’ve used K-Lite exclusively for 8-9 years now, and the N is from calcium nitrate, and my plants all look great.
 

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@ Ray
Several times you mentioned that the Huntington Botanical Gardens used calcium nitrate as a fertilizer. I would be curious to know what source of magnesium their plants use to make chlorophyll. Do they use tap water ?
 

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Yes, that is my understanding. It must contain a lot more minerals than my water does...
 
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