Glenna Partridge Garden Design If you do raised beds like these you must make sure you don't bury the tree under the soil. You could kill the tree if the trunk has too much soil around it. Smaller trees and shrubs can be dug up and raised to the proper level of the new raised bed soil. Maybe get a tree arborist (tree specialist) to come over and look at your trees. It's hard for me to give advice on trees that I have not seen. Another way to get some colour under large trees is to put containers in the beds or lawn. The plants won't have to compete with the tree roots and the container will be a sculptural element in the garden even when the plants are not in bloom. I hope this helps. Feel free to send some photos...I might be able to give you more advice on what to do. I hope this helps!