Tip from the test garden
To increase your success transplanting a shrub or small tree, root-prune two or three months before you move the plant. The process shortens long roots and encourages the formation of many new roots closer to the trunk, which help bind the soil during transplant.
1 Using a sharp spade, make 10-inch-deep vertical cuts in a continuous circle around the plant you plan to move. Start the cuts 10 to 15 inches from the trunk (use the greater distance for larger plants). Don’t remove soil, and avoid undercutting the rootball.
2 After two or three months, dig up the plant and move it to its new location. If you garden where ground freezes every winter, root-prune in spring and transplant in early autumn.