By: Bonnie L. Grant, Certified Urban Agriculturist
Winter is hard on plants. Cold weather damage to trees is sometimes obvious with broken limbs or it may be slow and insidious, not showing up until spring. The severity of the injury will dictate when to prune after winter damage. Learn the when and how to prune winter-damaged trees to reinvigorate and restore them to health.
The ideal time for pruning cold damaged plants, including trees and shrubs, is in early spring. This will give you a chance to observe whether the tree/shrub is in recovery and what, if any, limbs need to be removed. Cold weather damage to trees and shrubs occurs at many levels. If there are loose branches, remove them at the time of the injury to avoid hurting passers-by.
All other pruning should wait until the plant is out of dormancy. This is when you can tell whether a branch is still alive or if it requires removal. Remove no more than 1/3 of the plant material when pruning winter-damaged trees/shrubs. If more pruning needs to be done, wait until the following spring.
These tips will help when pruning cold damaged trees or shrubs becomes inevitable:
Pruning isn’t the only method of treating trees and shrubs with winter damage.
Provide good care and ensure the health of the tree/shrub is at its peak and most damage will not cause significant long-term problems. It is a good idea to prune young trees to create a strong scaffold and prevent top-heavy plants and unbalanced limbs. This helps prevent future injury and build a sturdy frame.
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Read more about General Tree Care
Fatsia (Fatsia japonica) shrubs are easily identified by their huge leaf structures depending on the soil conditions, the leaves can grow as large as 14 inches across. Since the fatsia's leaves are large, like sails, and grow up to 10 feet tall, this thick foliage plant can easily become damaged during winter storms. These lush shrubs are commonly found in U.S. Department of Agriculture's (USDA) hardiness zones 8 through 10 where winter damage is typically relegated to the northernmost zone areas. In fact, zone 7 can also be included if the plant is protected with a layer of mulch for freeze prevention. Several pruning methods are used to remove damaged branches for a healthy recovery in all hardiness zones.
For a natural look, use the technique known as "heading back." Eyeball the bush and locate the tallest main branch. With your eye and hand, follow this main branch until it meets a lower side branch that more or less points upwards. Cut the main branch off just above the smaller one. Repeat the process with this and all main branches, stepping back now and then—maybe even across the street—to assess the results. Prune slightly lower down than you feel really comfortable with remember, new growth will add additional height over the next six months.
For a major overhaul—removing 10 feet or more from a bush—use a saw on the main trunks, removing only a third of the height at each pass to prevent accidents.
Winter damage is not the only condition that causes boxwood leaves to turn brown and die. Boxwood blight also kills leaves on boxwood shrubs, and it is much more serious. It is a devastating fungal disease that rapidly spreads to nearby boxwood plants and can kill them.
If boxwood blight is present, it pays to know the early symptoms. They include:
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The explosive cracking sounds of trees crashing to the ground are sickening to the stomach. Whether it's damage from ice storms or sudden thunderstorms in the summer, trees require special care and should make a full recovery with little long-term injury.
Remove debris, then assess the damage
The first step is to make sure that there are no downed power lines or other dangerous elements.
Once you have deemed the area as safe, then the next step in caring for damaged trees is to remove all debris. This is mainly a safety factor, but also enables you to completely assess the extent of the damage.
Can the tree be saved?
Next, determine whether the tree can be saved. Most trees will be salvageable and will need time to recover. If there is heavy splitting of the bark and the cambium, growth layer is exposed, or the main trunk is split, the tree will probably not survive and should be removed.
Also, if there are so many broken limbs that the form of the tree is destroyed, replacement may be the best option.
Once it has been determined that the tree can be saved then pruning begins. Broken branches should be cut back to the next larger branch or back to the trunk. Never leave a stub when making a pruning cut. Stubs lead to rot and decay, and slow the healing process.
When cutting back to the next larger crotch or branch angle, do not cut flush with the branch. Instead make the cut in the area referred to as the branch collar. The collar is a transition area between the branch and the trunk. Cutting flush with the branch or trunk leaves a larger wound, which takes longer to heal. The collar area is raised with bark tissue, much like the crease on your hand where your thumb joins the other fingers.
Larger limbs should be taken off in stages. Cutting a large branch at once often leads to a strip of bark being ripped from the tree increasing the amount of damage. The following steps to removing large branches are:
Avoid "door knockers." Hire a local reputable tree company
Large trees are best handled by a reputable tree care service. Johnson County is fortunate to have many qualified arborists. When selecting a firm always ask for a certified arborist and never pay in advance. Quality companies will bill or collect after the work is completed.
Also, never allow the tree care service to use shoe spikes clipped to their work boots to climb your trees. Spikes cause damage, and/or can introduce disease into the tree. Spikes are only acceptable if the tree in question is going to be completely removed.
Topping is not a recommended practice of repairing storm damage. Topping weakens trees and makes them more susceptible to disease. If the damage is this severe then the tree should be removed. Also, no wound dressings are needed.
By taking the proper steps now the life and structure of the tree can be greatly improved for a full life.
Have questions? The Garden Hotline is staffed by trained EMG volunteers and Extension staff who will assist you with questions.
Not all plants should be cut back in winter. This is a list of plants that prefer to have their haircuts in late spring or summer.
Spring flowering shrubs – Forsythia, quince, azaleas, bridal wreath spirea and other shrubs that bloom in spring should be pruned immediately after they flower.
Spring flowering trees – Lilacs, ornamental fruit trees and Eastern redbuds, for example, should be pruned right after the tree finishes flowering.
Hydrangea macrophylla – Old-fashioned, pompon hydrangeas set bloom buds on the previous year’s growth. It’s safe to remove faded flowers and dead branches.
Once-blooming roses – Old-fashioned roses that only flower once each growing season, such as Damasks and moss roses bloom on old wood and should be pruned in the summer after they have flowered.
Gardenias – These should be pruned immediately after they bloom.
Bleeding trees – Maples, birches, dogwoods, walnuts and elms produce copious amounts of sap when they are pruned in late winter. Pruning won’t hurt the trees, but it will be less messy if you wait until summer.