Q. When is the optimal time to transplant evergreens and deciduous plants?
In the New York City area, USDA Zone 6a/6b (7), most deciduous woody plants can be planted and transplanted during the spring season between March 15 and May 1, before growth begins, or the fall planting season during dormancy between October 15 and December 1. Certain deciduous trees only transplant well in the spring planting season; some of these species include Beech, Birch, Maple, Oak and Sweetgum.
Evergreen trees and shrubs are best planted in the early spring between March 1 and April 15, prior to new growth, or mid- August through October 1 after growth has subsided and the ground is conducive toward easy root establishment. (Do not plant evergreens in late fall, as they will not have time to harden off before the damaging frost and winter winds arrive).
Transplanting is a shock to living plants and certain compensatory measures will help reduce the level of disturbance experienced by the plants. Judicious pruning at the time of planting will help compensate for root damage. Give appropriate attention to watering immediately after planting, and then frequently, to establish the new root system. Provide an organic mulch at the soil level, away from the trunck, to help conserve moisture.
Be sure that planting conditions are suitable; do not plant if the ground is excessively wet or frozen.
Courtesy of the NYBG Plant Information Service