Q: Is it safe to plant a pot-bound emerald green aborvitae in late January in central Virginia?
Tuesday, February 23, 2016
Q: I purchased three emerald green arborvitae for Christmas decorations this year, with the plan of planting them in the spring. All are very pot bound, and I want to know if it would be safe to plant them now (late January) in zone 7 (central Virginia), or should I wait?
A: You have asked two questions for which there are not good answers: when to plant, and what to do about the pot-bound condition? Both have to do with water relations. A new plant has only the roots it comes with, and they can only absorb water where those roots are--that is, in the root ball. Two factors complicate this: plants, especially evergreens, continue to use and lose (through transpiration) water in winter, especially if exposed to sun and wind. If the root ball is frozen, that water is not available to the plant. Generally, it is best to plant evergreens in early autumn or early to mid-spring.
At this point, it may be best to shelter the plants so they are out of the sun and wind until spring gets here. Group the plants and bury the root balls in mulch. Arborists see pot-bound roots as a long-term problem that calls for drastic actions. Take the plant out of its container and, using a pruning saw, make a series of vertical cuts to remove the outer 2 or 3 inches of circling root mass all the way the root ball. This stimulates the plant to grow new and normal roots into the surrounding soil. A caution here: all newly planted plants need water whenever the root ball starts to dry out because that is the only water available to them until they get established. So, a new tree might be on life support for some time, with the length of time depending on its size. Good luck with your plants!
Responder: Ed Milhous, RCA #350, Haymarket, VA