Using limestone Screenings to adjust PH for paphs, phrags

[Kawarthapine]

I usually add a combination of oyster shell and silica sand to tweak the ph and help improve leaf vigor amongst my paphs and phrags.

I'm out of my home-made mix and Paph Magic and wonder if anyone has tried adding simple landscaping grade, limestone screenings. Note: My mix typically includes coconut husk, sphagnum moss, charcoal and sponge rock/perlite. I don't let my plants sit in water unless I am away and replace medium every 12-18 months.

I have found lots of local, terrestrial orchids growing on and near limestone, but am not sure about application rates for the crushed, commercial variety.

Can anyone offer feedback, endorsements, cautionary notes, etc...

Many thanks!


Kawarthapine

 

[ALToronto]

It's actually a good source of a combination of calcium and magnesium. However, screenings from a construction gravel yard may be contaminated with salt and/or automotive fluids (not to mention cigarette butts and raccoon poop). If at all possible, bring your own bucket and shovel, and get the limestone that's below the surface of the pile. I would still soak and rinse it a couple of times, first with citric acid, then with plain water.

 

[abax]

or you could just buy Orchiata and get the cal/mag and less
K at the same time. Also don't have to repot so much.

 

[Ozpaph]

while the idea is good, I'm not sure how you will know if you use the right amount. I wouldnt experiment on a large number of plants with unknown ingredients.

 

[Bjorn]

Limestone is fine as main ingredient for paphs growing on limestone cliffs. I use it all the time in my mixes, but prefer to use the metamorphic types like marble or highly crystlline dolomite.

 

[gonewild]

I've used both oyster shell and limestone chips in side by side growing tests. Oyster shells were easy for me to purchase but limestone was impossible to purchase at a reasonable price. So I went to the mountains and collected my own limestone. I actually was hoping the chips would be produce some kind of dramatic improvement.

Limestone chips and oyster shell produce the same result, no noticeable difference.

 

[Happypaphy7]

Don't oyster shells take forever to break down??

 

[gonewild]

Don't oyster shells take forever to break down??

Not as long as limestone chips!

 

[Kawarthapine]

Thanks for the feedback.

For the record I purchase bagged limestone screenings from a local landscape store.

I also thoroughly rinse and wash screenings, and right before application I also rinse in a physan 20 solution to eradicate any unwanted pathogens.

I have decided to run a trial using same lighting, temps watering etc... I have several Memoria Dick Clements divisions.

I'm going to start by ph testing the water and medium and will then test ph (medium) every 3 months for a year and shall compare growth, vigor, flowering rates and anything else I can think of.

The real challenge is to try and find some info on the rate at which calcium is released and for how long it remains viable.

So many questions, so little time.

The irony is I got into this hobby as a distraction from work and yet here I am undertaking research and doing math and science, not my best subjects in school.

Again, thanks for the input.

Kawarthapine

 

[Ozpaph]

sounds like a useful experiment

 

[Mocchaccino]

Limestone gravel

I've used both oyster shell and limestone chips in side by side growing tests. Oyster shells were easy for me to purchase but limestone was impossible to purchase at a reasonable price. So I went to the mountains and collected my own limestone. I actually was hoping the chips would be produce some kind of dramatic improvement.

Limestone chips and oyster shell produce the same result, no noticeable difference.

I have to agree with Lance. I am so confused why these simple materials are so difficult to find.

I have been busy with my marine aquarium for 2 years and have merely kept minimal attention to my paphs, although 4 of them did bloom for me which made me embarrassed.

Back to the point, recently I have also been obsessed with the limestone issue. I searched over my local stores but failed to find one. I finally got one which is not intended for potting uses. It's so called limestone gravel intended to use as a condensate neutralizer for pool and spa. I believe you folks might well know about it. I know little about it since there isn't such thing in my city.



I don't want to act like a sales so I deliberately removed the brand in the photo. I made an enquiry to the company asking for the average sizes and chemical compositions. They replied CaO in majority. Sadly I have already purchased it online and shipping was on the way.



Anyway, I received the parcel yesterday. I tested it with basic chemistry. Since they claimed the major component is CaO. It should be highly soluble in water to give Ca(OH)2. I tested the water solubility. It did not dissolve after 10 minutes. I also tested it with lemon juice, of which the presence of CaCO3 should liberate gas. Yes, there was tiny gas bubbles when treated with fresh lemon juice (citric acid).



I agree the chemical composition is ill-defined. There is no guarantee on contamination. That's why I am going to use very minimal amount and am going to test them on cheaper and common paph species.

One word in mind, that parcel costed me a lot. It's 30 bugs for 1.8 pounds

 

[gonewild]

I agree the chemical composition is ill-defined. There is no guarantee on contamination. That's why I am going to use very minimal amount and am going to test them on cheaper and common paph species.

Looks like limestone to me. I would not have a problem using it in growing media.

 

[Falcon]

Try Coca Cola instead of lemon juice, it has phosphoric acid which will tell you right away as it is much more corrosive. Leave it go flat first to allow all CO2 to dissipate. The majority of stone where I'm from is limestone and this looks like a composite of limestone and something else from the photos.

 

[Mocchaccino]

Looks like limestone to me. I would not have a problem using it in growing media.

How much do you advise to add for those limy paph species? I am thinking of adding just a little or top dressing.

Try Coca Cola instead of lemon juice, it has phosphoric acid which will tell you right away as it is much more corrosive. Leave it go flat first to allow all CO2 to dissipate. The majority of stone where I'm from is limestone and this looks like a composite of limestone and something else from the photos.

It's kind of innovative. I wonder if it would cause precipitation due to the formation of CaPO4?

 

[Falcon]

It's kind of innovative. I wonder if it would cause precipitation due to the formation of CaPO4?

It should only be a short reaction as it will form Ca3(PO4)2 in situ which is insoluble anyway so only the outer layer will react. It should be enough for you to see if there is any reaction however. Worst case scenario here is that you've added extra drainage material giving more air to the roots

 

[gonewild]

How much do you advise to add for those limy paph species? I am thinking of adding just a little or top dressing.

Top dressing has a small effect, and if you water sparingly it has very little effect.
If you want to make a limestone environment in the substrate use more than 10% limestone chips and not more than 80% mixed in the media.