In some ways, this winter has been fairly typical. Our temps have yo-yoed, with periods of below-freezing and subzero days mixed in with random above-normal days. However, this winter is turning out to be one of the driest on record as rain and snowfall have eluded us.
With spring only about a month away, the office phone is starting to ring: Callers are concerned about their plants because of the fluctuating temperatures and dry conditions.
Predicting the amount of damage from the below-zero temps is difficult. The fact that we did not experience any rapid temperature changes last November or December might be a saving grace.
Damage in past winters occurred when the temps suddenly dropped and the plants were not fully hardened off or winter dormant. A plant is much more durable if it has had time to develop internally the processes needed to survive winter temperatures.
Some broadleaf evergreens are showing signs of discoloration and dehydration. For example, the large evergreen leaves of Magnolia grandiflora “Bracken Brown Beauty” are a rusty brown. This color change, while unattractive, should not have lasting effects on the health of the plant. The buds appear plump and healthy. The winter-burned leaves will drop later this spring as new growth appears.
I am concerned about our bigleaf hydrangeas, Hydrangea macrophylla. This includes the popular Endless Summer series. These hydrangeas produce their best flowers on old stems. The flower buds were set last fall. Low winter temperatures will damage and kill the terminal (or top) bud, which is the one containing the flower. If this bud is damaged, there will be no flower.
If you’re concerned about your hydrangea flower buds, the best approach is to wait. Do not prune or cut back bigleaf hydrangeas in the spring until you see signs of new growth. Cut back only to a live bud. Harder pruning except to remove dead wood could remove that all-important flower.
Winter’s effect on roses seems to vary depending on variety. From what I have seen, many of the easy care roses such as Knock Out appear to be just fine. But some varieties of hybrid teas have canes that appear blackened to the mulch level. Wait to prune roses until new growth starts to appear in late March, and then prune to remove all blackened growth.
Lastly, the main concern for this winter is dry soil. Evergreens and less established plants are most at risk. The full effects of winter drought on evergreens won’t start showing until summer. By that time it is too late to save the plant. Take advantage of any warm winter days and get the hoses out. This same weather pattern occurred a few years ago, and we lost a number of pines and spruces.