Winter Damage in the Garden
Barbara Leach, Horticulture Technician, VCE - Roanoke
Winter damage in the garden comes in many forms. It can come from vacillating temperatures that can kill marginally hardy plants or even those that would otherwise take colder temperatures but cannot take the vacillation. On the way to the trashcan the other day, I noticed my evergreen rosemary looking decidedly dead. Sadly, I think the damage has moved beyond simple discoloration. Sometimes it is just discoloration, however. Some broadleaf evergreens may even defoliate, yet re-foliate in the spring. Others will hang onto the discolored foliage and produce new spring growth to cover it. The damaged leaves may drop the following year. Sometimes it is a wait-and-see game. If a plant has not shown any signs of re-foliation by summer you should likely replace it. Shrubs may die back all the way to the ground like an herbaceous perennial and re-sprout with all new canes. In these cases, it is always wise to fertilize in mid-spring. If fertilized too early they may break growth while there is still a danger of more damage from weather. We can use some of the principles we have learned about pruning to our advantage in early spring. If unsure whether a cane is dead, you can remove the tip back to an outward-facing bud. This removes the hormone that controls apical dominance (is telling that bush not to branch out.) That gives the lower buds a better chance to break growth if they are still alive. Hydrangeas are a good example if this. They will often break leaves around the bottom of the canes and up a few buds, but the tips never re-foliate. You simply give the basal growth a chance at a good start before removing all the dead tips. If time passes and you still have seen no basal growth on the canes, there is still a possibility that, like a crape myrtle, it will just grow all new canes. Remove the old ones completely. The new canes will need thinning. Don’t let them all develop or your shrub will be too dense.
Other plants may experience ice or snow damage, or be damaged by vehicles or people. Sometimes, in the case of a very young tree, it is better to cut it off at the ground and let a new trunk develop than to try to splint a broken trunk. Not all trees will re-sprout if sawn off. Many of our native trees; willows, ash, elms, hornbeams, sycamore, mulberry, osage-orange, beech, birch, oak, and redbuds are good candidates for rejuvenation. Most conifers are not. Other factors play into this, like age, health, and conditions. When deciding whether to cut a tree off or not, consider the purpose of the tree, your ability to provide after-care and your willingness to take a chance. If it is a front lawn specimen, consider replacement if it is not salvageable. However, if it were a redbud that got snapped off along the roadway it is worth trying to cleanly cut it off and let it regenerate. Try not to leave a stump. Be assured it will re-sprout with many sprouts if it re-sprouts at all. It will require after-care in the form of water and you cutting out all sprouts while very young, except one. This will be an ongoing task over the next several years but, eventually, sprouts will quit coming. If all of the stored energy goes back into one sprout it will regenerate at a surprising rate; much faster than a newly planted tree can grow.
If only part of the top sustained damaged, there are many pruning options. Remove damaged portions to a sound side limb suitable for training into a new top. Remove cracked or twisted limbs. Even if splinted or bolted, most limbs will never recover sufficiently to be strong, but there is a possibility that new limbs can be encouraged as replacements. In the case of a small rounded shrub like a boxwood or azalea, having a whole portion shortened after snow or ice damage, you want to pinch the tips on the short side to encourage new growth (using that apical dominance rule again) and reduce the size of the larger side with as few cuts as you can. This discourages lots of growth on the heavy side that will make the shrub even more unbalanced.
If you need help deciding how to handle your winter damage, call the Roanoke Master Gardeners at (540)776-7178.