Protecting Willows from Wind and Frost

Understanding the Risks

Willows are generally considered deciduous trees well-adapted to cold winters — they go fully dormant, drop their leaves, and experience no physiological activity through the coldest months. However, several specific winter conditions cause damage that accumulates over successive seasons.

Winter Desiccation

Even in dormancy, woody stems lose moisture to dry winter air. In the prairies and interior BC, where relative humidity can fall very low in winter and wind speeds are high, this desiccation can cause bark splitting and tip dieback on exposed outer branches. Young trees with thin bark are more susceptible than established specimens. The phenomenon is sometimes called "winter kill" but is more accurately a desiccation injury rather than direct frost damage.

Late Spring Frost

Willows leaf out early — often before the date of the last average frost in their region. This makes them susceptible to late frost events that can damage or kill newly emerged leaves. A hard frost at this stage is rarely fatal for established trees; the tree will produce a second flush of leaves from dormant buds. However, in young trees in their first or second year, repeated late-frost damage can set back establishment significantly.

Ice Load

Ice storms, particularly common in Ontario, Quebec, and the Maritimes, deposit significant ice weight on branches. Willow branches are flexible but can snap under sustained ice load, particularly on the outer canopy of large weeping specimens. The long, pendulous branches of weeping willows act as collection surfaces for freezing rain, accumulating more ice than upright-branching species.

Frost Heaving of Young Trees

Newly planted willows, particularly those put in during autumn, can be partially lifted from the soil by freeze-thaw cycles. The expanding soil pushes the root ball upward, breaking newly formed root connections. Trees showing frost heave in spring should be pressed firmly back into position before the soil dries and the roots are left exposed to air.

Site-Based Protection

The most effective protection is provided before the tree is planted, by choosing a site that naturally mitigates the relevant risks.

Using Existing Windbreaks

Placing willows on the lee side of existing shelter — a hedge, fence, building, or a row of established conifers — significantly reduces the desiccating effect of prevailing winter winds. In most of Canada, prevailing winter winds come from the northwest; planting on the southeast or east side of a windbreak takes advantage of this. The willow should be close enough to benefit from the shelter but not so close that it competes for root space or is shaded from summer sun.

Creating New Shelter

On open lots where no existing shelter is available, establishing a windbreak of fast-growing conifers — such as white spruce (Picea glauca) or green ash (Fraxinus pennsylvanica) — before or at the same time as planting the willow can reduce wind exposure within three to five years. This is a longer-term investment but one that improves conditions for all garden plants on the property.

Mulching for Root Protection

Applying organic mulch — wood chips, shredded bark, or straw — around the base of a willow before the ground freezes reduces the depth and rate of soil freezing, which moderates root zone temperatures and reduces the risk of frost heaving. A layer of 8–12 cm is sufficient. The mulch should extend to the drip line of the canopy if possible, covering the full root zone rather than just the immediate trunk area.

Mulch must be pulled back 10 cm from the trunk to prevent moisture and organic matter from being held against the bark, which encourages rot and provides habitat for overwintering insects that feed on bark.

Protecting Young Trees from Wind

For newly planted willows in their first two winters, temporary wind protection can reduce desiccation injury on exposed sites. Burlap screens staked around the tree on the windward side — not wrapped tightly around the branches — intercept wind without trapping excessive moisture. Remove these screens in spring once temperatures are consistently above freezing.

Plastic tree wraps are sometimes used on the trunks of young trees to prevent sunscald — a condition where bark is warmed by winter sun on cold days and then damaged when temperature drops rapidly after sunset. White or light-coloured wraps reflect solar radiation. These should be removed in spring to prevent them from trapping moisture against the bark through the growing season.

After an Ice Storm

After an ice storm, resist the urge to shake ice off branches. Ice-loaded branches are brittle; the mechanical shock of shaking causes more breakage than leaving the ice to melt naturally. Assess for broken or hanging branches once the ice has cleared, and remove any that present a safety risk with clean cuts at the branch collar.

If a large limb has split from the trunk, the wound should be evaluated by a certified arborist rather than left open or treated with pruning paint — the latter is no longer considered beneficial under current arboricultural practice. Davey's guidance on post-storm tree care covers the decision process for storm-damaged trees in more detail.

Late Frost Response

When a late frost is forecast after leaf emergence, temporary protection with a breathable frost cloth can reduce damage on small or newly planted willows. Weighted at the edges to prevent wind displacement, frost cloth traps ground heat around the canopy. For large established willows, physical protection is not practical; the tree will recover from leaf damage without intervention. Avoid fertilising a frost-damaged willow until it has produced a new flush of growth and appears to have stabilised.

Last updated: May 22, 2026