Mir-Acid (30-10-10) was invented by Dr. O. Wesley Davidson of Rutgers University many, many years ago in response to nitrogen deficiency caused by the microorganisms that break down bark.
Keep in mind that a lot has changed since then. For one, most bark-based media are changed more frequently, so the breakdown is less of an issue. The bark itself is typically treated in some way, which can reduce the microorganism population. We also use less "from the yard" additives - dry leaf litter used to be a staple, and that certainly dragged "bugs" into the medium.
As we no longer typically have to deal with a nitrogen deficiency, the use of Mir-Acid will end up being the application of excessive nitrogen, which can stop blooming altogether, if used continuously.
Personally, I use it on my azaleas and rhododendrons only, but if you use it during early growth periods, then switch to a low-nitrogen formula as the growths mature, it should be OK to use on orchids. I'm too lazy to track the need for formula changes, and with my varied collection, things are never in growth-cycle synchronization, so i stick the the MSU formula year round.
|