I used to think that the only time to plant or transplant was in the spring. This is true for strawberries and raspberries but not always for trees and shrubs. Spring and fall are both good times to transplant. Certainly, there are some plants that are best and most successfully moved in the spring. However, there is little documented research to show success or failure rates regarding when one transplants. The obvious exception would be planting in mid-summer and mid-winter when success rates are very low.
One area of confusion is the difference between planting and transplanting. Planting is literally placing a plant in the ground on what will (hopefully) be a permanent site. Transplanting involves digging up a plant from one site and relocating it at a new site. When planting is done, theoretically, no roots are lost. When transplanting is done, the majority of the trees or shrubs original root system is cut off during the process.
Autumn, especially early through mid-autumn is an excellent time to transplant many trees and shrubs in Minnesota. This is because there is aggressive root growth occurring below the ground in the fall. The autumn soil temperatures and moisture content in most of the Minnesota landscape are ideal for root growth.
The loss of roots during the transplanting procedure normally creates a health condition to plants called transplant shock. The condition is not as serious as the term implies. In fact, the majority of the transplanted trees and shrubs fully recover in a relatively short period of time. During this shock period, the root system must recover from the loss of some roots by re-establishing the root and shoot balance. As the plant recovers, the tree or shrub shows restarted growth above the ground.
During this recovery period, as the tree or shrub is growing, it is more vulnerable to stressful weather and landscape conditions that healthy plants can normally tolerate. Short term drought, hot and windy weather, and early deep freezes can result in some abnormal damage to plants. Whether the plant is a native one or an introduced one, they are all vulnerable to transplant shock.
Healthy plants transplant more successfully because it takes a lot of the plant’s stored energy to establish a new root system. If the plant is unhealthy, it probably has a very poor energy reserve system. Also, an unhealthy plant may have a small canopy (branches with leaves). It may also have a lot of branch die-back and decay in the stem. If the plant is infected with boring insects, it’s probably not a good idea to transplant that tree or shrub.
— Jerry Vitalis is a Chisago County Master Gardener