I have a large, mature tree peony that I would like to move. Since the roots will be damaged, do I prune the top growth of this 4-foot shrub? When is the best time of year to do this?
Christopher Michalek, Lake Zurich, IL
David Furman of
Cricket Hill Garden
, which specializes in Chinese tree peonies, replies: Tree peonies have an expansive root system, so expect to lose a large percentage of the root mass. To improve your tree peony’s chances of survival, root-prune it after it blooms in late spring to encourage a healthy, compact, and easily moved root ball. Using a sharp, straight spade, dig about 1 foot straight into the ground, forming a circle around the plant. You should do this at the drip line, which is indicated by the outer spread of the foliage.
Transplant in fall, when your peonies are dormant. Begin by digging a trench around the plant, working just beyond the drip line where you did the root-pruning. Next, insert a pipe underneath the plant and, using it as a fulcrum, force the plant up with as much of the root system as possible. This is not a process you can be gentle with; have someone strong help you.
Once the plant is out of the ground, evaluate the root system. Tree peonies may have either tap roots or fibrous roots. Those with tap roots are the most difficult to transplant. Prune back the foliage by at least half—more if you weren’t able to pull up much of the root mass. Remove leaves and old growth. Heavy pruning will reduce the stress on the root system, as roots must be capable of absorbing water and nutrients to support the entire plant.
Plant tree peonies in a well-drained location in partial sun, allowing 5 square feet for it to grow. Dig a hole 2 feet wide and at least 2 feet deep. After placing your peony in the hole, add good garden soil and water thoroughly to eliminate any air pockets, then add additional soil as needed after it settles. A good layer of mulch will help protect it through the winter.