Trees for Tennessee Landscapes - Maintaining and Protecting
Most trees experience shock after transplanting because of the disturbance to the root system. In balled and burlapped (B&B) transplants, it is estimated that 4 to 9 percent of the original root system and about 2 percent of the soil volume occupied by the root system in the nursery is contained in the root ball (Watson 1994). Trees try to keep a balance between the above-ground portion of the tree and the root system (Perry 1982). When the amount of the root system is reduced during transplanting, the above-ground portion of the tree is also affected. The tree either is stimulated to regenerate more roots to balance the top, or the top partially dies back, or both so that the shoots and the roots establish equilibrium.
Although containerized trees have a complete root system when transplanted, the container has limited the volume and extent of the root system. Because of restricted root development, most container plants are watered daily before transplanting. The roots in the planting medium of the container act as a wick during water uptake, only drawing water from the container medium. The differences in water potentials between the planting medium and the native soil will either take water away from the container medium, causing water deficits, or draw water toward the container medium, causing saturation and limiting oxygen to the roots. At either extreme, water uptake is limited. The solution is not to have water potential extremes between the native soil and the container medium. Water must be available to the root system at all times to allow the roots to expand from the medium to the soil.
Thus, transplanting success depends primarily on the care of the root system before and after transplanting. It is important for roots to gain access to the native soil from container-bound and B&B plants.
"Sp574 Post-Planting Tree Care - Fallacies and Recommendations," The University of Tennessee Agricultural Extension Service, SP574-15M-12-00 R12-4900-21-006-01, http://trace.tennessee.edu/utk_agexfores/69