I am trying a product known as The Silicon Solution, brand name Pro-Tekt by Dyna-Gro. Jim mentioned that some members of his orchid club were using it, in our thread back in May about SuperThrive. The claims are that it enhances resistance to cold, other environmental stress and fungal attack by strengthening the plants' cell walls.
I did some reading up on it at that time and it sure sounded like something that would help me grow orchids outdoors, so I bought a bottle and have been spraying it once a month in my fert spray since maybe June. As the weather gets cooler and drier, I'm going to put it in the weekly douse, too. Time will tell. My first stab at the silicon research netted an interesting article
https://njaes.rutgers.edu/spot... although this study used calcium silicate as a soil amendment, not silicon dioxide (that's in Pro Tekt) as a soluble additive. The most interesting tidbit is that silicon has been accepted as a "plant beneficial substance" and plant available Si can be listed in the "Guaranteed Analysis" on fertilizers since the Rutgers study, I think it was.
I definitely plan to try it out on my veggies this fall, too. It was shown to boost resistance to powdery mildew disease in the study - and boy! do I get powdery mildew around here in the fall!
I hear you about the trees over the orchid area. One of my big oaks tends to reach over my pool cage where the orchids are. I am hoping the thorough cleaning of the cage two weeks ago has eliminated at least a little of the tree 'dirt' that falls. I have pruned the branches back faithfully, but the rainwater I use to water my 'chids comes off the roof where those branches overhang, too. So that may be another source. One more thing I've noticed is where the snails were getting onto some plants, those plants definitely have more black spots, so the goldurned snails must have been spreading it around in their travels. I have not seen another snail on the 'chids since we installed the copper door sills, though.