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This is a discussion on when to use booster fertilizer within the New Growers: Ask the Senior Members forums, part of the New Growers category; Originally Posted by Plantcrazed101 I use dyna-grow foliage pro fertilizer... I thought the foliage pro ...
There is nothing wrong with Foliage Pro. It is a 9-3-6 product, and does contain both calcium and magnesium, in addition to the trace elements, which is excellent.
The key is to focus on that nitrogen content: think of nitrogen as "calories" in our diets. Let's say that to be healthy, one needs 2000 calories a day, and we have two foods to choose from - one that's 2000 calories per plate, and another that's 500. In order to get the proper nutrition level, we could eat one plate of the first, or 4 of the second. Fertilizers are analogous: to match the nitrogen in my use of 12-1-1, you'd need 12/9=1.33 times as much.
Having said that, I believe that more important than formula is the mass of nitrogen applied. That is, the concentration used and frequency of application. Orchids are some of the lowest consumers of nutrition in the plant world, and feeding is definitely a case of "less is more".
The fact is that NOBODY really knows what the plants need. Instead, it is common for scientists to look at tissue samples, and surmise the formula from that. Unfortunately, that paints a poor picture, because what's in a plant has very little bearing on what it needs.
Some nutrients are taken up passively - if it's available in the environment, it'll be in the plant. If it's there in high concentration, it will be high in the plant, and vice versa, so the tissue analysis tells you about the environment, not the requirements of the plant. Plants also have nutrient "pumps" that actively absorb nutrient ions and sock them away in cell vacuoles, "saving them for a rainy day" when the outside supply is insufficient. Potassium is one of those minerals that are stored in excess, so unless you're providing essentially none, the tissue analysis will invariably show relatively high levels in the plant - again, not a measure of what's needed. In my talks to orchid societies I point out that if tissue analysis was an accurate measure of what's needed, I obviously need high cholesterol!
That's why we decided to try the "what's in the environment" approach, and went with a rough estimate of the average "throughfall" and "trunk flow" analyses we gathered, knowing that it's just a guess as much as the tissue analysis, but coming from a different direction. So what we, and mega-corporations like Monsanto, do is hypothesize, test, and observe.
I'll throw in a little more insight that I've learned recently: it also helps to know something about the geology of the area the plants come from. The example I was given by Alan Koch of Gold Country orchids was that rupicolous laelias tend to grow where the ground is just loaded with iron. The trees in those forests will absorb that iron, and it will be in a relatively higher concentration in the leaf exudates that wash down to the laelias when it rains. Hence, they ought to do better in captivity if we increase the iron content of our fertilizer solutions by adding a bit of iron sulfate, or the like.