Early spring, just before the buds break, is the best time to plant and transplant many kinds of trees and shrubs. It's not long before root growth occurs, so there's little chance of too much drying out before new roots can get moisture for the plant. But professionals pland and transplant almost any time of the year, even during the heat and drought of summer. With today's know-how, the number of plants that can't be moved in the summer is small.
The worst time is late spring, when the plants have tender new growth that will wilt quickly if there is the least deficiency of moisture. "I am convinced that anti-transpirants are a definite asset in summer transplanting of woody plants," says Francis Gouin, University of Maryland ornamental horticulturalist.
"Trees thoroughly sprayed with a good anti-transpirant [such as Vapor Gard or Protect 400W] just prior to digging are slow to wilt," showing that anti-transpirants do keep water vapors from leaving the foliage.
Many vacationing gardeners have discovered that anti-transpirants can reduce the need for plant-sitters, Gouin says. Watering a plant well and spraying the foliage thoroughly with a good anti-transpirant eliminates the need to water for a week or two.
For successful transplanting of trees and shrubs during the summer, soil moisture must be abundant and available. If the soil is excessively dry or wet, delay planting until more favorable conditions prevail.
Sometimes it's nearly impossible to move a large plant without damage to the root system. Pruning the tree or shrub before moving it will improve its chances of survival in the new location. Prune each branch to a natural form to preserve the plant's natural shape. When plants, especially evergreens, are moved in the fall, see that they get plenty of soil moisture in the winter so that early winds won't dry them out before roots are functioning. Watering during winter thaws is beneficial if the soil is dry, especially with evergreens, and the use of windbreaks is frequently justified.
Those safely moved in the spring are the magnolias, yellow poplar, yellowwood and sassafras.
In the summer, after growth hardens, English boxwood is as easy to move as it is in the spring or fall. The hollies are much like boxwood in this respect, particularly American holly. Abelia, nandina, evergreen barberry, wax-leved privet and Pieris japonica all transplant easily and stand the heat during summer, but keep them watered.