I am sorry for this delayed reply to your gardening question. We are transitioning to a new Q&A system and your question was unfortunately lost in the transition. I have discovered it now and hope this reply is not too late to be of help.
Your magnolia needs time to recover and adjust to its new environment. The black mold is normal in an outdoor setting. The fact that new growth is occurring is a good sign. The buds should stop dropping in time. There is no need to do anything to the tree especially since it is so large and well established by now.
Thanks for the question. Please stop in again soon!
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