green and black mildew or mold

[78Terp]

Now I am not advocating putting it out, in the open, in the pouring rain. But shelter above it with anything to help deflect a portion of the water is the thing to do. And don't let it sit in pools of water. Get it off the ground.

I use a 6 inch, clip on fan.

[raybark]

Ray, with the low P do you still get good blooming? I read that it isn't the amount of P but the kind you use that matters.

I actually am getting better blooming than I've seen in years, although I'm certain part of that is the significant reduction in nitrogen provided, and may not be attributable to the formula itself.

Phosphorus actually plays a bigger role in leaf and root growth than it does flowers. The supposed relationship to blooming is likely an offshoot of the myth about high-P "bloom boosters", which actually worked not by phosphorus content itself, but through the addition of inexpensive P-compounds to the formula, the nitrogen was diluted, lowering its concentration, and "allowing" the plant to bloom normally.

About 90%-95% of an orchid is water. Of the remaining dry mass, roughly half is carbon, with nitrogen, oxygen, and hydrogen existing in the 1-5 percent levels. P, K, Ca, Mg, & S are in the next tier, at 0.1%-1%, with everything else being in the ppms.

That was part of the basis for testing the K-Lite formula, but I'm actually not that big of a fan of using tissue analysis as a guide. For example, a plant will take up as much K as it is given, through "pumps" that offset normal osmotic pressures, so the high K content of a plant does not mean the plant "needs" it. If tissue analysis was a good indicator of need, then I obviously need more cholesterol!

[sciencegal]

I like the scientific explantion, Ray.

This might explain my first experiences last year with the phals. I bought some MSU fertilizer and the instructions said feed weakly weekly. I didn't know at the time that the dosage recommended was weak, at least that's what they told me. I was using about 1/4 strength in order for it to be weak.

From what you are saying the recommended dosage is not weak but the P level at the recommended dosage is only 3 or 4%. If I fed weakly (1/4 dosage) then it was reduced to practically nothing. However, the phals bloomed great for me which is how I ended up getting addicted to orchids. Maybe I will try the K-lite since the K level is pretty high. Sheesh. The accessories for the orchids cost more than the orchid itself.

[raybark]

Being a scientist and engineer myself, terms like "weakly", and "1/4 strength" drive me nuts, as they have absolutely no meaning. It's sort-of like "How high is up?".

When the MSU fertilizers were first publicized in the AOS Orchid article, they stated that they used 125 ppm N weekly (about 1.25 tsp/gal). I followed that example, but as I feed at every watering, sometimes fed the plants 2 or 3 times a week. When I asked the guy that invented the formula how they arrived at that dosing level, I was told that "it was not scientific at all - they [the folks at MSU] tried it and it seemed to work".

K-Lite is actually a derivative of the MSU formula, and I have been using it at about 25 ppm N, still at every watering, so with the ratios being 12.9% N, 1.3% P₂O₅, 1.3% K₂O, I am feeding at 25 ppm N, 1 ppm P, and 2 ppm K.

[kdennis14]

Thank Y'all for sharing your knowledge!!