Michelia alba air layering
Several month ago, during summer, I started trying to propagate my Michelia alba by air layering. I've tried it on three separate branches and so far I have yet to see roots. All three branches are alive and healthy and all of them have big calluses at the cut end, which I assume is a good sign.
My questions are: how long should I expect to wait to see roots? Is it possible I might just see exponential callus growth and no root formation? Will periodic brushing with rooting hormone help?