Winter is a good time to prune trees and shrubs
UNIVERSITY OF MINNESOTA EXTENSION - www.extension.umn.edu
February and March are good months for pruning some of our woody landscape plants. By now, trees and shrubs are dormant. The ground is also solidly frozen, making it easier to reach branches and remove them. And with the exception of evergreens and oaks, they have dropped their leaves providing a clear view of their structure.
Why we prune plants
Examples of good branch cuts. Notice the donut-like ring left after the branch is removed. This is the collar and it is important for healing over the wound.
- We prune to improve plant form.
- Pruning allows for the removal of dead or dying branches as well as branch stubs and branches injured by disease, severe insect infestation, animals, storms, or other mechanical damage.
- Crossing branches tend to rub against each other and develop wounds. These wounds allow for disease and pests to get under bark and into stems, causing issues for the plant down the road.
- Pruning opens up tree canopies, increasing airflow and light to stems and branches.
- More light means more flowers, leaves and fruits.
- More light and air reduce moisture and potential disease caused by bacteria and fungal pathogens.
When to prune
Late winter is a good time to prune most plants. Because plants and their pests are dormant this time of year, pruning cuts can be made without the risk of pests and pathogens entering the tree through the wound.
What plants can be pruned now?
A shrub in need of pruning
- Crabapple, apples
- Mountain ash
- Butternut and walnut
Evergreens like spruce, pine and fir rarely require pruning. However, spruce can be pruned in late winter as can arborvitae, juniper, cypress, yews and hemlocks in late winter or early spring. Loosely shear dense evergreens like arborvitae by removing just the newer growth. This allows for light to reach the inside of the plant.
Deciduous shrubs that can be pruned now:
Renewal pruning - the removal of about ⅓ of the stems - is a good way to keep new stems growing and maintain the form of the shrub.
- Alpine currant
- Burning bush
- Purpleleaf sandcherry
Late winter is not the time to prune spring-flowering shrubs like lilacs, magnolia, juneberry, azalea, etc. Prune now and you will remove the flower buds meaning fewer beautiful blooms in the coming spring. Wait to prune these plants after they bloom (within two weeks).
For a list of these plants and more pruning information: Pruning trees and shrubs.