Ask the master gardeners
Q: When is the best time to transplant?
A: While it is technically true that all plants can be transplanted, it is equally true that some do not like to be moved once established. Younger plants transplant better than older, shrubs better than trees, and deciduous plants better than evergreens.
Observing a few guidelines will ensure that a transplant will succeed. Besides the timing of transplanting, the gardener must consider the light, soil pH, moisture needs and wind exposure recommended for the particular plant. Also, the transplant site must take into account the size of the transplant at maturity. Orienting the plant in the same direction relative to the sun as it was previously will help the plant re-establish.
Remember that transplanting causes stress, which you want to minimize as much as possible. If you want to transplant in spring, it must be done after the ground has thawed and before the plant has started to bud out. If you wish to transplant in the fall, it should occur after leaf drop but before the ground freezes. A transplant will likely not survive if it has budded out in the spring or if it has not had time to become established in the fall prior to ground freeze.
It is generally easier in the Northeast to transplant in the spring because budding out can be clearly seen while the time of ground freeze can be capricious.
The condition of the root system is vital. Remember that roots provide moisture to all other parts of the plant, they anchor the plant and they produce hormones that control the plant’s growth. Obviously then, a plant with a severely damaged root system will not transplant well.
Smaller plants should be transplanted as bare roots, ideally in the spring. Take care to spread out the roots, pruning any that could possibly entangle or circle the plant, thereby girdling and killing it. Larger plants must be transplanted with soil attached.
The planting hole should be two to three times the width of the root ball. Water the plant thoroughly prior to transplant and keep it well watered after it’s been moved. A 3- to 4-inch layer of mulch will help conserve moisture.
Judie Phillips, master gardener, Cornell Cooperative Extension of Westchester