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 The risks of frost damage to trees and woodlands is likely to increase under climate change, even though temperatures are likely to rise and a decrease in extreme winter cold is expected.

This is because milder winter weather can delay or prevent dormancy and hardening off in some tree species, leaving them more vulnerable to damage from frost and periods of extreme winter cold. Milder spring weather will cause earlier flushing which increases the risk of frost damage.

Frosts can affect all aspects of growth and reproduction, impacting timber quality and increasing susceptibility to disease. Reducing potential for frost damage, particularly from late spring frosts in a changing climate is important as the climate warms.

Frost risk

Most native woodland species will be tolerant of the cold temperatures that typically occur over winter in British conditions and introduced tree species will have been selected on appropriate tolerance for typical past climate conditions. However, the warming climate has already reduced the frequency and severity of frosts and increased the length of the frost-free season in many areas, and this trend is projected to increase. 

Trees are particularly vulnerable to cold temperature episodes if they occur outside the period that trees are dormant or hardened. Milder winters may delay or prevent full dormancy, increasing the risk of damage or mortality from autumn frosts, severe frosts and periods of extreme cold. Milder springs may lead to bud-break, flushing and growth earlier in the season, increase the risk of damage from late frosts. 

Impact of frost

  • Extreme cold periods can damage plant tissues and lead to die-back or tree death. The increase in stress may affect tree growth or make trees more susceptible to disease.
  • Frosts may cause damage to sensitive new growth or de-hardened shoots in spring or early summer (late frosts), or to the current year’s leaves in autumn (early frosts) before leaf fall or shoot hardening.

Risk factors

  • Frost risk tends to be highest inland and lower in coastal areas.
  • Frost pockets or hollows and north-facing slopes are at higher risk, this can be exacerbated if there are light, sandy soils where the surface cools more rapidly.

Adaptation measures

A selection of appropriate tree species, provenance and seed origin can reduce frost damage. Avoid frost-sensitive or marginal species, especially in vulnerable locations.

Decision support tools

There are a range of online tools to assist managers in assessing risks to forests and woodlands, and selecting appropriate adaption measures.