ok...here ya go.
while studying s/h, i believe that i read that air roots (those that are mounted) act in a different way than ground roots. so if you want to mount stuff, wait for new root tips. that being said, a greenhouse environment is warm and moist, which is conducive to root growth, so maybe it doesnt matter if theyre growing new roots or not.
not very helpful, right?
maybe you could do a couple of test orchids?