Many seek tips regarding how to prune arborvitae, whether generally or, specifically, after a shrub has suffered branch damage in winter due to the build-up of snow and/or ice. I answer both questions below (the answer is more or less the same for both sets of circumstances, although, if your shrub does not suffer any damage, you may well skip pruning altogether).
Reader Skipandwanda grows arborvitae shrubs that suffered damage over the winter and wanted to know how to deal with the damage through pruning. My answer may well help you solve a similar problem in your own landscaping.
"My arborvitae took a beating this winter. Should I cut the ones that are bent from the top and, if so, how? As for the ones that have lower branches bent outward, should those branches be cut off? Will they fill in eventually? Should the ones that took a beating overall be cut just above the soil (I guess they call this rejuvenation pruning) or should they be removed?"
My answer follows.
How to Prune Arborvitae
Arborvitae is sometimes pruned so as to grow with a single leader, in which case extraneous leaders are pruned off entirely (right back to the trunk). If your arborvitae is young, it may not be too late to train it in this fashion. The ice or snow damage caused some leader branches to become "bent from the top" on your arborvitae, as you put it, so this gives you an opportunity to assess your "leader situation."
While we never enjoy seeing such damage, there could be a silver lining. The damage provides you with just the excuse you need to target these bent branches as extraneous leaders and trim them off, leaving in place only the straightest leader.
If, however, your arborvitae shrubs are already several years old (or if all the potential leaders have already become bent due to shouldering excessive snow and ice), it is too late for such pruning. You could, however, try to straighten them out by tying branches together with strips of cotton fabric (perhaps in conjunction with staking).
When pruning lower branches, remember:
- Do not prune back further than where you see stems with green foliage (unless you can live with not having a branch there at all, in which case you would prune right back to the trunk).
- Bare arborvitae branches will not sprout new growth.
The best time for pruning arborvitae shrubs, generally speaking, is late winter or early spring. If you are using them in a hedge, you will perhaps want to shear them in late spring or early summer, as well (keep the top of the hedge narrower than the bottom, so that the lower branches receive sufficient sunlight).
As for the "ones that took a beating overall," I would remove them and start with fresh, appropriately-sized arborvitae stock. Rejuvenation pruning (whereby plants are pruned almost to the ground, in hope that they will come back anew) is not an option here, as it is for some deciduous shrubs. Even in the case of shrubs responsive to rejuvenation pruning, such as lilacs, your planting will be out of balance for years, with relatively tall plants (the ones you left alone, more or less) intermixed with the ones drastically hacked back. Therefore, growing new plants is preferable (find out the best times to plant trees and shrubs).
Does It Help a Damaged Shrub to Fertilize It?
Some gardeners wonder, "The following spring, should I be fertilizing plants damaged in winter to help them recover?" It is a valid question, so I will conclude this article with a look at whether fertilizers are helpful in healing sick or injured trees.
Fertilizing is generally not recommended as a way to help damaged shrubs recover. Fertilizer is most productive when a tree or shrub is healthy enough to absorb it properly; that is, fertilization is more about “feeding” (or helping a plant take up nutrients more effectively) than “healing.”
You need to allow your damaged arborvitae shrub some time to heal. Wait until you see the injured plant leafing out (signifying a return to health) before fertilizing.
In the meantime, check the wounds to make sure no fungi are exploiting it in its weakened condition.