I am sorry for this delayed reply to your gardening question. The spring rush has brought a deluge of questions and we are working hard to catch up!
Adding that much soil will be deadly to those trees. I am not sure there is a solution as even if you leave a fairly large area around them uncovered it will be stressful due to the area that is covered. They would need at least an area extending 10 feet out in all direction around them to be left uncovered.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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