Transplanting
Any plant which is root bound, ( by root bound I mean so many roots that have taken on the shape of the pot) needs to be removed from that pot. Once removed take a serrated knife and slice down the sides of the root system. Then with your fingers tease those roots outward ( not so much as to damage the tree).
This will help to encourage outward root growth.
Plant the tree at the same level it sat in the pot, and make the planting hole slightly larger ( a 12" tree could use a 20-24" hole)
Then water according to your areas needs.
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John,
Garden Visions Nursery
ISA certified Arborist, Illinois Certified Nurseryman