We do go back to fertilizing with regular fert every 5 days for the rest of the month, Ursula. It's evidently just when you are supplementing with Mg that you want to use the potassium nitrate.

Now I'm confused. The UF fertilizer formulated for palms (8-2-12) contains 2% phosphoruus and 4% magnesium. That is the palm fertilizer recommended by UF and the Extension Service and is the fertilizer I use exclusively on all of my trees and shrubs. I think it works great. Also, we have tons of phosphorus occurring in the ground here in Florida so how do we add magnesium at all? I don't want to take issue with Mr. Motes but this doesn't sound right to me.

Jim

I will leave all this to you Florida folks to figure out. I am unsure how much science is behind all this theory. It is enough for me to just "fertilize". I rotate through four formulae, but I sure don't have science behind what I use or when I use it. I have so many plants, it is hard enough just to water on a regular basis.

LOL, I am going back to read that chapter on cation exchange capabilities.

We have near toxic levels of phosphorus here too. The only rocks we ever find in our soil are chunks of phosphate.

You do know if you are buying potassium nitrate Big Brother will be watching you very carefully.

Yes, I thought of that, Alice. Since I am not even an American citizen, I hope they don't think I am planning terrorist acts. I only bought a small packet of it, too.

The foliar feeding of soluble ferts for orchids is what Mr. Motes is getting at, with the Mg binding to phosphorus in the sprayer before it reaches the orchids' roots and leaves, I guess. He does recommend also mixing all soluble fert with rain water or otherwise purified water to remove the possibility of phosphorus that is very likely in our tap water, too. It's for certain going to be in my well water. Don't forget, both his books are specific to growing orchids in Florida. Other places don't necessarily have the phosphorus issues that we have.

I had trouble getting the reddish tints out of the leaves of some of my hanging orchids last spring, but now that I realize I was watering them with the well water, it makes more sense. In summer they hardly get any well water, so they aren't getting a dose of phosphorus as often. Going to have to turn off the auto sprayers a day or so before I fertilize and supplement from now on. Life is never simple with orchids, right?

The phosphorus in the ground is available to terrestrial plants, but that's why your palm fert has such a low middle number, Jim. Most ferts that are formulated for Florida have that low Phosphorus number. If you want to supplement garden plants in the ground with Mg, I think I'd go for spraying dissolved Epsom Salts as a foliar feed rather than sprinkling it on the ground. Plants potted in potting mix (no phosphorus in the soil) well I've been supplementing my Brugs for years with a sprinkle of Epsom Salts.

I buy magnesium sulfate in 50 lb. bags and sprinkle it around palms and other plants that show signs of older leaf chlorosis. I've been happy with the results. If that doesn't work, I've really been fooling myself and worse, giving out bad information. I need to check this out. I know plants will not take up iron if the soil is too alkaline so I have sprayed liquid iron on the foliage and had success. This magnesium thing is big news to me and it shouldn't matter if we are talking in the ground or in the tank.

Jim

I wonder if the Phosphorus needs to be dissolved - that is, in solution - to bind the Magnesium? In that case, sprinkling the (very soluble) Magnesium on the top of the soil where it is dissolved by rain or irrigation probably gets it to at least the uppermost roots of your palms before the Phosphorus has a chance to react with it?

Wow! am learning a lot and slightly overwhelmed. all I really know how to use are the recommended better grow orchid fert, I just recently used slow release too.

For non orchid plants I only use miracle gro and SuperBloom. I still have a lot to learn.

I was confused on it too so now I am just combining the Mg with my liquid seaweed fertilizer as it has a zero P number.

I need to read and re-read to fully absorb the information. And remember that sometimes books are edited and a vital piece of information could be left out (this is especially true with scientific information in layman books).

So true, editors are usually English majors, not scientists - or gardeners. Just re-wording a sentence can change meanings.

Ha, I thought Dr. Motes is surely no English major, and he sure didn't pay anyone to edit his books. There are spelling and grammatical errors everywhere in both his books. But he does have a PhD in something, wait! Hoo Boy! Turns out he IS an English major, as he was an assistant professor of English at Wright State University . . . who knew?? So, at least he is a gardener, but not a scientist. At least we know he knows how to grow great orchids.

Anyway, here are the pertinent passages:
"Two facts stand out from this study: orchids need less phosphorus than previously thought and they need more magnesium than they usually get. This new approach to orchid nutrition has particular cogency for us in South Florida where our ground water sometimes contains phosphorus (particularly on the West Coast) and almost without exception, is highly alkaline. The high pH of our ground water in combination with phosphorus in fertilizer binds up most of the metallic trace elements, including magnesium."

The study he refers to is the research begun @ 2003 at Michigan State University to develop better formulations of fertilizer, specifically for orchids. He also says later "Mature plants in general require less phosphorus because it is an element plants tend to conserve, and transport from older tissue to newer growth." So his advice is to only use "bloom booster" fert that is high in phosphorus for a couple of feedings in the spring when plants are growing roots and getting ready to develop blooms.

Later on, in the Vanda book he says he also 'shocks' some of his Vandas with a dose of bloom booster in the fall around the time the first cold front is forecast, because Vandas often put on blooms in response to the temperature change.

dyzzypyxxy said:Ha, I thought Dr. Motes is surely no English major, and he sure didn't pay anyone to edit his books. There are spelling and grammatical errors everywhere in both his books. But he does have a PhD in something, wait! Hoo Boy! Turns out he IS an English major, as he was an assistant professor of English at Wright State University . . . who knew?? So, at least he is a gardener, but not a scientist. At least we know he knows how to grow great orchids.

Anyway, here are the pertinent passages:
"Two facts stand out from this study: orchids need less phosphorus than previously thought and they need more magnesium than they usually get. This new approach to orchid nutrition has particular cogency for us in South Florida where our ground water sometimes contains phosphorus (particularly on the West Coast) and almost without exception, is highly alkaline. The high pH of our ground water in combination with phosphorus in fertilizer binds up most of the metallic trace elements, including magnesium."

The study he refers to is the research begun @ 2003 at Michigan State University to develop better formulations of fertilizer, specifically for orchids. He also says later "Mature plants in general require less phosphorus because it is an element plants tend to conserve, and transport from older tissue to newer growth." So his advice is to only use "bloom booster" fert that is high in phosphorus for a couple of feedings in the spring when plants are growing roots and getting ready to develop blooms.

Later on, in the Vanda book he says he also 'shocks' some of his Vandas with a dose of bloom booster in the fall around the time the first cold front is forecast, because Vandas often put on blooms in response to the temperature change.

Ah, yes. That was the passage I remember. I need to double check our soil and water samples, because Memphis is not alkaline. We tend to be more acidic. Will revert back.

But if you dissolve fertilizer in a sprayer, and it has phosphorus in it, that will raise the pH. I'm going to do some more pH tests on my 3 types of water (tap, rain, and well) and also maybe test the pH of the various fertilizer solutions I'm using.

It may be enlightening. In any case, who doesn't love an experiment.

I just read through the Dr Motes' paragraphs addressing somewhat higher Phosphorus contents in Florida's water, coupled with alkaline pH.
It makes sense that you don't need to add as much Phosphorus if it is present already.
(Fair Lawn doesn't list any, I just checked )
Normally in acidic water you would have H3PO4, but depending on the alkalinity in Florida water you would have one, two or all three Hydrogens ionized, replaced by Mg.
So, for Florida's water this makes sense.

for sharing your info! Hmm I need to pay attention to what I'm feeding my plants.

Hmmm, my blue got done blooming already so our first cold front (below 70s for me is cold) is usually late November/December. So by then my blue Vanda would have rested 3 months already.

I read online though that sometimes Vanda will not bloom for a year if it is exposed in a cold weather....but no info on what "cold" means...below 40s?

I bring my Vandas in when the temps hit upper 50's. And I'm a bit further north than you, I think! 70's for me is cold too! Thinking that I need to move further south!

Good Tara, I will bring them in when it hits upper 50s too! I don't want to wait another year for it to rebloom.

I found this in Link:

https://www.aos.org/Default.as...

I have encouraging news, ladies. In Dr. Motes' Vanda book he says some Vandas will bloom 3 times per year! In fact . . . I'm pretty encouraged by my one little yellow mini-Vanda that has now bloomed twice this summer.

I agree with the mid-50's to bring them indoors, but if you can keep them in a sunny place, and give them lots of water and food as well, there's hope for more flowers than what we've had.

Um, Gigi sometimes we get the first "cool" front in October, I think. But you're right, the first really cold weather - days in the 70's - is usually November at the earliest. It's the night time temperatures you've got to watch for, as far as the orchids are concerned.

Two months ago I stated that for the first time ever (in perhaps ten years of growing), my Vanda had bloomed three times. That was all within a 4-5 month period. Perhaps I will have further blooming this fall/winter?