Answer: The way I am reading your question you plan on placing the bed around the diameter of the tree, between 6 inches and 1 ft. deep. Correct? How far out from the trunk do you plan to extend? If you weren't going to extend very far outward, and the bed wasn't much deeper than 6" you would probably be OK. It also depends on what type of tree you are planting around. You probably aren't going to hurt a massive Silver Maple by planting in this way, but I wouldn't try it with a tree thatdoesn't have that type of fortitude. The reason I ask how far out you want to come is because the farther out from the tree you come with the soil, the more tree roots you are affecting. In general, it isn't a good idea to add additional soil at the base of the tree because trees are used to receiving air, water and nutrients at a certain level, and by adding new soil, you change their environment.
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