Transplanting is a delicate process that ideally occurs during dormancy, at the beginning or end of the growing season. In the Arnold Arboretum’s nurseries, we use traditional methods to ball and burlap our field-grown trees. To preserve the proper ratio between roots and shoots, we measure the diameter of the trunk: for every inch, we need a minimum root-ball diameter of fifteen inches. Because we cannot input every factor into an equation, we also exercise judgment, accounting for the tree’s height and the anatomy of its root system.
Once we have determined the diameter, we sever the roots with a sharp spade and excavate a trench. The root ball should be deep enough to ensure that taproots are retained—at least 65 percent the diameter. We shave away excess soil to minimize transport weight. The exposed root ball is wrapped with burlap and secured with sisal, using a drum-lacing pattern. We carefully rock the tree, freeing it from the soil below. At this point, the tree is ready to go.
15:1
The proper ratio between the root-ball and trunk diameters.
65 percent
A root ball must have a depth of at least 65 percent its diameter.
Chris Copeland is Greenhouse Horticultural Technologist at the Arnold Arboretum.