Chilling requirement

One of the impacts predicted for climate change is milder winter temperatures.
Most of our major fruit producing regions are planted with varieties selected to match the temperatures typical for each region. Low chill varieties for regions with mild winters, medium chill and high chill for regions with cold winters.

What will happen with these varieties if average winter temperatures increase into the future?

Many of these varieties may not receive sufficient winter chilling to produce viable crops. The amount of cold needed by a plant to resume normal spring growth, following the winter period, is commonly referred to as its ‘chilling requirement.’

Plant species as well as horticultural varieties vary widely in their winter cold requirement.

---Topics in this article---

  • What happens during winter chilling
  • Measuring winter chilling
  • Result of insufficient winter chill
  • Use of dormancy breaker Dormex to substitute for lack of winter chill
  • Anatomical changes within buds during chill accumulation
  • Sectioning buds
  • Application


  • Table 1. Chilling requirements for fruit types
  • Table 2. Typical symptoms of insufficient winter chilling. The results have been verified in other USA States.
  • Table 3. Chilling information for use in applying Dormex to peaches in Alabama.