Climate patterns have changed in recent years. Winters are shorter, milder, and less predictable, which can be a problem for trees.
Trees rely on winter dormancy to reset and prepare for healthy spring growth. Climate impacts on tree dormancy, like disruptions in chilling hours and temperature swings, can trigger long-term stress.
How Tree Dormancy Works
Generally, there are three stages to tree dormancy: acclimation, deep dormancy, and deacclimation.
- Acclimation is the preparation period when trees make necessary adjustments, such as leaf drop, to get ready for winter. Trees use the photoperiod cues of shorter days and cooler temperatures in the fall to trigger this stage of dormancy.
- Deep dormancy refers to when trees enter a “deep sleep” during the winter to accumulate a certain number of “chill hours.” Tree chilling hours happen when temperatures fall between 32 and 45 degrees Fahrenheit and help trees survive the deep frosts of winter.
- Deacclimation is the period when trees have accumulated enough chill hours and enter “standby” mode until the spring.
How Climate Change Is Disrupting Dormancy
Tree dormancy and climate change are closely connected. Fewer hard freezes cause dormancy disruption in trees and incomplete shutdown, which can affect spring growth. Warmer early winters can cause early bud swell in trees.
Inconsistent temperature changes also create unpredictable rainfall and drought cycles, which can stress roots during dormancy. Trees can also experience frost damage from warm winters with late cold snaps.
What Trees Are Most at Risk
Some tree species are more susceptible to the climate’s impact on tree dormancy, including:
- Fruit trees – Species like apple and peach trees need consistent chill hours. Fruit trees that missed chill hours are less likely to flower in the spring.
- Flowering ornamentals – Trees like magnolias and redbuds are more sensitive to temperature shifts.
- Evergreens – Evergreen trees may restart sap flow early, which risks bark splitting.
- Broadleaf evergreens – If these species experience water loss, they can be susceptible to root damage.
What You Can Watch for This Winter
While you can’t control the weather, you can certainly protect trees during warm winters. Look out for these signs of dormancy disruption in trees this winter and spring:
- Swollen buds during a warm spell
- Flowering too early
- Leaves or needles appearing prematurely
- Bark cracks or sunscald on trunks
- Missed or stunted spring blooms
How to Help Trees Cope with Changing Winters
Warm winter tree care can help mitigate climate impacts on tree dormancy. Here are some tips to protect trees during warm winters:
- Mulching regulates root temperature
- Watering during dry spells, especially for evergreens, can help avoid drought stress
- Installing protection, like tree wraps, on sun-exposed trunks to prevent cracking
- Scheduling winter inspections to assess bud health and damage
- Implementing plant healthcare programs to strengthen roots and boost post-dormancy recovery
What Professional Arborists Look For
Certified Arborists ® can easily spot impacts from dormancy disruption in trees. During an inspection, arborists typically look for early dormancy break signs like bud swell, damage from fluctuating soil temperatures, repeated bloom failure, and species-specific dormancy failure patterns.
Frequently Asked Questions
Trees don’t typically start new above-ground growth in the winter, but if soil temperatures are around 32 to 40 degrees Fahrenheit, roots can continue to grow slowly. Warmer winter spells can cause bud break, but subsequent freezes can damage those buds.
Trees that require extended periods of chilling hours, like fruit trees, are most affected by disrupted dormancy patterns. If they don’t receive enough chilling hours, fruit trees can experience irregular budding, low fruit set, and be more susceptible to frost damage.
Consistent deep watering before freezes, mulching to insulate roots during temperature swings, and protective wrappings can help protect trees during a warmer winter.
Yes! Certified arborists can spot early signs of damage caused by dormancy disruptions.
Your trees may be waking up before they should. Don’t wait for spring to spot the damage. Schedule a winter tree inspection to ensure they’re on track for a healthy season.
HOW DO COLD TEMPERATURES AFFECT SPRING GROWTH?
