University of Manitoba - Faculty of Agricultural & Food Sciences - Frost and Winter Damage
Frost and Winter Damage

Problem type: Environmental

Name of problem: 
Frost and Winter Damage

Plant name(s): Evergreen and other woody trees and shrubs

Symptoms / Characteristics:
Common symptoms caused by winter freezing are dieback, foliar browning, sunscald, and bark splitting near the base of the trunk. Dieback of twigs and branches and frost cracks occur when warm temperatures, quickly followed by cool temperatures, kill active tissues inside the plant. This also applies to sunscald injury. Trees with smooth bark, such as cherry trees, are more susceptible to sunscald, which produces cracks along sun exposed trunks and branches.

Winter injury can generally be attributed to one of three factors: desiccation, freezing and breakage. The breakage of limbs is usually due to a combination of ice, snow or wind. Ice and snow can create substantial weight on branches, causing even large, strong branches to break. Branches covered in ice become very brittle and can snap if bent the wrong way.

Desiccation refers to the drying of foliage, which is one reason why evergreen trees and shrubs experience winter browning. Evergreens continually transpire water from their needles, but roots are unable to replace that lost water if the ground is frozen.

Frost heaving can also be detrimental by damaging roots and even pushing new plantings out of the ground. Plants can also undergo severe mammal damage during the winter as animals forage for food.

Control / Preventions:
Plants susceptible to sunscald can be wrapped with a light colored material to reflect light. Wraps should be put on in the fall and removed in the spring after the last frost. Sprawling tree branches on evergreens can be tied together to reduce chances of snow and ice build up. Weak branches and multiple leaders can be pruned to reduce the chance of breakage as well. Entire evergreen trees and shrubs can be wrapped or protected by barriers from desiccation and sun exposure. Leave the top of covers open to allow some air and light to penetrate.

The use of mulches can greatly reduce injuries related to winter damage. Mulches insulate the soil, keep soil temperatures from fluctuating and help conserve moisture in the soil. If soil is dry before winter, there is a much better chance for damage than if it is sufficiently moist. Moist soils hold more heat than dry soil and will provide moisture to plants requiring it. Soil temperatures lower much more slowly than air temperatures, and plants still need water through the fall. Watering should be slowly decreased going into fall to harden plants off, but a good soaking should be given before freeze up. Avoid any cultural practices that will initiate new succulent growth, as new growth will only be damaged and needed energy will be wasted. Plants need to prepare for winter and that is what their energy should be put towards. A little extra attention given in the fall can help plants overwinter and start spring in good condition.