I see you are new to the Forum.. Welcome ! Happy to have you join us.
There are many answers to your question, and some of them would be related to where you are located, and the conditions there.
If you identify where you live, country or State, and what type/species of orchids you are growing under the tree, we would better be able to help you.
I, for example live in Barbados in the Caribbean. I can grow some terrestrials in a garden bed, and some other types attached to trees. Most everything else is either potted or mounted.
I am sure others will be along to give their opinions, but in the meantime tell us where you are.