# Crushed oyster shell top dressing Paphs



## Anca86 (Mar 13, 2021)

Hello,

Do Paphs need crushed oystershell top dressing?
Thanks


----------



## musa (Mar 13, 2021)

Paphs need some form of CaCO3, first to regulate the pH-value, second as a source of calcium. In nature many Paphs grow on limestone (not all!). What form you use, oyster shell, egg shell, dolomite powder limestone gravel, marble gravel... is up to you, whatever fits best to cour culture and conditions.


----------



## Anca86 (Mar 13, 2021)

musa said:


> Paphs need some form of CaCO3, first to regulate the pH-value, second as a source of calcium. In nature many Paphs grow on limestone (not all!). What form you use, oyster shell, egg shell, dolomite powder limestone gravel, marble gravel... is up to you, whatever fits best to cour culture and conditions.


Thank you for your reply


----------



## Ozpaph (Mar 13, 2021)

i mix some up in the potting mix.


----------



## richgarrison (Mar 13, 2021)

i do both, some in the mix as i repot, and finally a top dress... chicken grit (sometimes referred to a as oyster shell, although it isn't 100% oyster shell)... i pay 10$ for a 40lb bag at my ag supply. 

and while you are at it, Orchid Zone back in the day was a fan of including some sand in their mixes. The sand they used was the sand used in pool filters, not just any sand. Not very much, but i sprinkle a little of that in the pots as i am repotting also... 

Putting that stuff in the mix itself and then repotting, in my experience, has lead to most of it sitting in the bottom of the mix container, and not very much making it into the actual pots... Hence me adding it as i repot. Makes the repotting exercise feel a little more like cooking


----------



## Happypaphy7 (Mar 13, 2021)

It is not necessary.
The whole adding oyster shell/dolomite to the potting mix thing came from the fact that many species are found in the wild where lime stone is very common. Often, the entire area!
While many species have their roots on direct contact with the rock itself, the roots are often covered with many organic debris and dirt as well as live moss. Others are not in direct contact with the rock at all where there is a layer of soil and organic matter over the rock bed in which the roots grow. The pH at the root zone is actually near neutral or slightly acidic.

Now, some Paphiopedilums I purchased came with little bit of crushed oyster shell mixed in the potting mix.
Others (almost all) came without any of that. They seem perfectly fine either way. When I repot them, I do not use oyster shell or lime stone.


----------



## werner.freitag (Mar 13, 2021)

the calcium is just one part of the puzzle
and it is in the mix, in the fertilizer , in the water and...............


----------



## SuperPaph (Mar 13, 2021)

I use to add small limestone pieces in medium, besides a small quantity of crushed shells, which will stabilize the adequate pH near roots, and will act like a "tampoon" stabilizing, excusing the repetition.


----------



## abax (Mar 13, 2021)

Might it just be easier to use K-Lite?


----------



## Ray (Mar 14, 2021)

The simple fact is that plants must have a source of calcium while in active growth. That calcium must be in ionic form in solution in order to be taken up by the plant.

Look at the water solubility oyster shells, limestone, gypsum, dolomite, marble, egg shells, etc., etc., and compare them to that of calcium nitrate, which is used in many fertilizers. Relatively speaking, they are quite _insoluble_.

That said, there are two things that stop me from saying “they don’t work”. One is the fact that the mass of calcium ions needed is not huge, and the other is that none of those potential supplements is totally insoluble, so they must be contributing _something_. My question is “is it enough?”, and rather than risking a deficiency, I think it’s better to use something I know contains a truly soluble source.


----------



## Anca86 (Mar 14, 2021)

Ray said:


> The simple fact is that plants must have a source of calcium while in active growth. That calcium must be in ionic form in solution in order to be taken up by the plant.
> 
> Look at the water solubility oyster shells, limestone, gypsum, dolomite, marble, egg shells, etc., etc., and compare them to that of calcium nitrate, which is used in many fertilizers. Relatively speaking, they are quite _insoluble_.
> 
> That said, there are two things that stop me from saying “they don’t work”. One is the fact that the mass of calcium ions needed is not huge, and the other is that none of those potential supplements is totally insoluble, so they must be contributing _something_. My question is “is it enough?”, and rather than risking a deficiency, I think it’s better to use something I know contains a truly soluble source.


Thank you, Ray
I asked because I just received a Paphiopedilum appetonianum and I've read that one must put a top dressing of oyster shell.


----------



## SuperPaph (Mar 14, 2021)

Ray said:


> “they don’t work”.


You are right, but calcium in substratum keep it with not low pH, neutralizing the acidity.


----------



## Brabantia (Mar 14, 2021)

Materials that contain Calcium such as dolomite, crushed shells, coral ... should not be considered as sources of Calcium but rather as neutralizing agent of the the substrate acidity which develops with the aging of the substrate.


----------



## Anca86 (Mar 14, 2021)

SuperPaph said:


> You are right, but calcium in substratum keep it with not low pH, neutralizing the acidity.


What would be a good ph for paphiopedilum?


----------



## Brabantia (Mar 15, 2021)

Anca86 said:


> What would be a good ph for paphiopedilum?


I would say between 6.5 and 7. If, despite the addition of basic substances, you notice that the pH remains acidic (typically 5.6 or lower) , I advise you to repot in a fresh substrate. Your substrat is too decayed.


----------



## Anca86 (Mar 15, 2021)

Brabantia said:


> I would say between 6.5 and 7. If, despite the addition of basic substances, you notice that the pH remains acidic (typically 5.6 or lower) , I advise you to repot in a fresh substrate. Your substrat is too decayed.


Thank you for the information.


----------



## Ray (Mar 15, 2021)

Be aware that the pH of the solution you apply is not likely to play a very great role in the pH of the medium, and that's what's important.

If you want to know the pot pH, do the "Pour-Through" test:


Water the pot with your solution-of-choice.
Wait 30 minutes, allowing the pot to thoroughly drain and for the chemistry to equilibrate.
Trickle about 50 ml (I use a shot glass, as it's quite handy) over the surface of the medium and collect the drainage.

THAT's the pH to test.


----------



## Anca86 (Mar 16, 2021)

Ray said:


> Be aware that the pH of the solution you apply is not likely to play a very great role in the pH of the medium, and that's what's important.
> 
> If you want to know the pot pH, do the "Pour-Through" test:
> 
> ...


Thank you,Ray.


----------



## Anca86 (Mar 16, 2021)

Ray said:


> Be aware that the pH of the solution you apply is not likely to play a very great role in the pH of the medium, and that's what's important.
> 
> If you want to know the pot pH, do the "Pour-Through" test:
> 
> ...


Hi Ra


Ray said:


> Be aware that the pH of the solution you apply is not likely to play a very great role in the pH of the medium, and that's what's important.
> 
> If you want to know the pot pH, do the "Pour-Through" test:
> 
> ...


So...today I measured tge ph for my paphs and phrags. For paphs I got around 7 with a max of 7,15. For Phrags, also around 7 but the mas is 7,40. I don't quite know what to think about this.


----------



## Ozpaph (Mar 18, 2021)

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?


----------



## Ray (Mar 18, 2021)

Ozpaph said:


> 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 (Mar 18, 2021)

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???


----------



## Ozpaph (Mar 20, 2021)

i postulate that the longer contact time makes the measurement more accurate.


----------



## Ray (Mar 20, 2021)

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.


----------



## Ozpaph (Mar 22, 2021)

sounds like im using the 'saturated media' method.


----------



## Stone (Apr 6, 2021)

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.


----------



## Ray (Apr 7, 2021)

Stone said:


> 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.


----------



## papheteer (Apr 7, 2021)

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


----------



## Ozpaph (Apr 7, 2021)

papheteer said:


> 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


that's interesting - how much and how often?


----------



## Stone (Apr 7, 2021)

Ray said:


> 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....


https://www.fs.fed.us/wildflowers/plant-of-the-week/images/hartstonguefern/asplenium_scolopendrium_americanum_lg.jpg










Asplenium ceterach - The British Pteridological Society


Rustyback Fern Asplenium ceterach on a wall in Oxford A perennial small wintergreen wall fern, often known by the name Rustyback due to the appearance of the back of the … Continue reading Asplenium ceterach →




ebps.org.uk


----------



## Stone (Apr 7, 2021)

papheteer said:


> 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.


----------



## papheteer (Apr 8, 2021)

Ozpaph said:


> 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! 


Ozpaph said:


> that's interesting - how much and how often?


----------



## papheteer (Apr 8, 2021)

Stone said:


> 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.


----------



## papheteer (Apr 8, 2021)

Stone said:


> 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.





Hen Express Poultry Oyster Shell (Crushed) - 2.27 Kg (5 lb.) Bag : Amazon.ca: Pet Supplies


Find thousands of pet supplies at low prices. Shop online for dog, cat, fish, bird, and small animal supplies at Amazon.ca



www.amazon.ca





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


----------



## Ray (Apr 8, 2021)

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.


----------



## Ray (Apr 8, 2021)

Stone said:


> 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....
> 
> 
> https://www.fs.fed.us/wildflowers/plant-of-the-week/images/hartstonguefern/asplenium_scolopendrium_americanum_lg.jpg
> ...


Thanks!


----------



## Stone (Apr 8, 2021)

Ray said:


> 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.


----------



## Ray (Apr 9, 2021)

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.


----------



## Brabantia (Apr 10, 2021)

@ 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 ?


----------



## Ray (Apr 10, 2021)

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


----------

