'What Orchids Eat', importance of calcium
 

When I read the article ‘What Orchids Eat’ by Rick Lockwood, two points I took away from it were that calcium is a very important mineral for growing healthy orchids and that potassium blocks the uptake of calcium. I realize he was talking about the possible long term toxicity of excess potassium also, but I’ve heard several growers talk about the importance of calcium recently, so I keyed on that point. Our water has lots of calcium in it but one expert told my orchid society that the calcium in our water is not a type that is readily available to plants. Rather than using a low potassium fertilizer, I started applying a calcium/magnesium supplement, at first once a month, and more recently twice a month. I do not mix it with fertilizer so there’s no potassium in the mix. After using a calcium/magnesium supplement for almost a year, I’ve noticed two improvements in my plants. One, the bud drop problem that has plagued me for years has almost completely disappeared. Second, the fungus problems that I've always had during long rainy summers in South Florida have been non-existent this year. I know this is only antidotal evidence, but I've been very impressed with the results so far. The product I use is called MagiCal and it’s designed for hydroponics. I use it at 1 teaspoon per gallon, twice a month, by itself. Not mixed with fertilizer. I think it’s worth a try, especially if you have problems with buds failing.

This is a complicated matter, I haven't taken a botany class at this kind of level before, but I think it has something to do with how a cell functions and ionic balances and such.

I don't know if your speaker went into the scientific details or not, because the material might be very dry and go over way too many people's heads, so I'm sure he went over what he felt was important to horticulturists/hobbyists.

I'm just learning about how important the following ions are to the functioning of a human being's entire nervous system: K+, Na+, Ca2+/Ca++, Mg2+/Mg++, Cl-. There could be something of this nature happening with plant cells as well, but again, I'm not 100% certain of the details because I haven't taken a botany class at this kind of level yet.

This whole imbalance between K+ ions and Ca2+, and Mg2+ ions in accordance to proper plant cell function, is probably what your speaker was addressing.

But I think you did the right thing by not reducing the amount of available K+ ions, but rather, increased the available Ca2+ ions. Just as we need K+, so do plants. To totally eliminate K from the picture will eventually do more long term harm than good. Reduction of the K+ ion, might also cause long term issues as well, idk.

That was an interesting article, and there's a thread on that subject which I'm planning to jump into after it cools off a little. It hasn't been active lately so maybe now is the time.

By coincidence, we had already gone from using straight MSU to less MSU + some CalMag + some micros, which since we start with RO water has the effect of increasing the concentration of Ca and Mg and reducing K (and P), before reading the Lockwood article, and were/are pretty happy with the results. Not drawing any conclusions yet, just saying .... I've since bought a small bottle of the K-Lite from Ray which we're trialing.

Alan Koch, whose advice has generally worked very well for us, is a big believer in the value of plenty of calcium for orchids, especially in the form of dolomite. He feels it's harder to burn plants with dolomite than other forms. In the one conversation I had with him about the potassium issue, he was not in favor of reducing it, though we didn't have time to discuss it in much depth. In addition to all of his growing experience, one of his degrees is in plant physiology, an area I'm just starting to study.

Steve

The bit about potassium "blocking the uptake" of calcium is not necessarily an "at that moment" thing, that is, not mixing your Magi-cal with fertilizer may not be the fix you think.

Potassium binds very well and preferentially with plant tissues and with potting media. Unless it's fresh, your potting mix might have tons of K in it anyway.

Interestingly (to me anyway), Rick's original hypothesis came from his studies related to toxicity in molluscs - not plants at all. When I started discussing it with him, I started to see parallels with the mineral systems used in ceramics, which is more my field, and that's what gained my "buy in" - with some skepticism.

Some of my recent findings - thinking simply in terms of chemical systems and energy states - puts me WAY out on a "suppositional limb": When an ion goes into solution, energy is released [FACT], so I am assuming that in order to extract that ion from the (fertilizer) solution, the plant must pump some energy back in [SUSPICION ONLY - but it makes some sort of sense]. Potassium happens to have one of the lowest enthalpies of solution of the mineral ions, suggesting that the plant has to expend less energy to take it back out of solution again, hence giving it preferential uptake, at the expense of others.

Those are excellent points, Ray. Thanks.

Preferentially to what? Not preferentially to calcium or magnesium.

This is an interesting discussion (I believe I read the same article, in "Orchids" Magazine?)... Can't wait to read more from y'all! :biggrin:

Wierd question tho, can you use dolomite lime as a source of calcium? (can it be mixed w/ water to do this?)

I haven't used dolomite myself but I know some growers do, especially for paphs.. Here's an article where the author mentions using dolomite.

http://www.staugorchidsociety.org/PD...ps-Calcium.pdf

---------- Post added at 03:37 PM ---------- Previous post was at 03:35 PM ----------

It just occurred to me, as I watch a tropical storm move into South Florida, that much of my water during the summer comes from rain. I grow outdoors and it rains a lot in Ft. Lauderdale. Rain water doesn't have any calcium in it and that may be one reason that I see good results when I use calcium.

Exactly why I said "way out on a limb", David.

If you look ONLY at the enthalpies of solution, and "buy" the supposition about the plant needing to release energy in order to "extract" the ions from the solution, then yes, the K would be absorbed more easily than the Ca or Mg.

In my many years of working in the glass, ceramic, and chemical industries, as well as the time I have taught in college, I find it useful to simply "spit out" concepts. Sometimes they are right, and more frequently they are not - but they often give someone, somewhere, a new mental direction they had not been considering or addressing, and coupled with other knowledge, often lead to interesting and useful understandings and discoveries.

So you are saying that your statement that "Potassium binds very well and preferentially (compared to calcium and magnesium) ... with potting media" was just speculation that is probably wrong? I would go farther and say that that statement is almost certainly wrong.