I apologize for this delayed reply to your gardening question and hope it is still helpful to you.
If it is just a small area you can build up your bed with no problem. Just keep from piling dirt up against the tree's trunk. If it is going to mean covering an area extending 10 feet or more out from the tree you may want to try and go only about 2-4 inches deep with the soil you add to make the bed.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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