After this, you will need to prune the roots every two to four years. Winter or early spring are the best times to prune the roots. You have to cut off about two to four inches from the bottom of the rootball and cut out three or four one-inch wedges from the side of the rootball. This will encourage the maple to send out new rootlets.
Remember to keep the roots out of direct sunlight as much as you can while transplanting. Good luck!
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