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This is a discussion on calcium and magnesium within the New Growers: Ask the Senior Members forums, part of the New Growers category; Puppies2, I also observed a positive change in my orchids when I lowered the pH ...
Puppies2, I also observed a positive change in my orchids when I lowered the pH of the water I use for fertilizer and supplements. I read a book on phalaenopsis culture that claimed that lowering the pH was one of the quickest and easiest ways to improve the health of your plants.
Ditto...I simply love the blossoms. Also, I feel a sense of accomplishment for healthy looking plants, new roots and leaves. I love starting out the day with a cup of coffee and admiring the beauty and intricacy of these wonders before heading out the door
---------- Post added at 10:43 PM ---------- Previous post was at 10:39 PM ----------
Wow, that's interesting. Was the author of the book Eric Christenson? I'm reading it now.
His favorite is Vietnamese orchids and find this forum, my english will not be as good as you on here, you empathy for
Dolomite is a natural blend of Calcium carbonate and Magnesium carbonate, it's essentially a gentle limestone.
"Optimal for orchid growth" may be way too specific. Different plants live in environments with different substrate pH levels. Anything from 5.5 to 6.5 will be fine for most, and if you go a bit outside of that, they'll be fine, too. Even the low-7's isn't "bad".
Let me also add that it really isn't the pH of the solutions that's important; it the pH of the substrate the roots live in that is, and the substrate often overwhelms that of the solutions.
Ray, how would you measure pH of media?!
Also what is the lowest pH og solution orchids will tolerate. I noticed that adding kelp extract (super thrive at least) at recommended dose lower pH as low as 4.5. My home water (long island, ny) has ph 6.5. So i was windering if 4.5 is too acidic for orchids?
Svetlana, the classic approach to measuring substrate pH is to collect the runoff at the time of watering, but with non-soil media, that's a bit tricky, as a large-volume pour-through really doesn't have time to interact with the medium, and any that does is diluted.
The best test I've seen so-far (and I'm open to other suggestions) is to water your plants normally, wait an hour or two, then trickle a little plain water over the surface, collecting the runoff for testing.
As to "what's too low", I think we need to remember that pH, alone, doesn't paint the whole picture. Pure water, once exposed to the air, has an equilibrium pH of about 5.4, thanks to the absorbed carbon dioxide forming carbonic acid. But H2CO3 is such a weak acid that it is overwhelmed by the substrate and whatever else you put into the water. If I add a little citric acid, the pH will go even lower, but the same applies. The alkalinity (acid buffering capacity) of the solution is really what matters, especially in conjunction with the pH. If your water pH "gives" so easily at the addition of something like SuperThrive (which is not a kelp extract, by the way), it's pretty low in alkalinity, so I wouldn't worry about it.
I use RO water, and once I add fertilizer, my starting solution pH is about 5-5.3, and I simply don't worry about it.