Temperate fruit trees — peaches, apples, pears, cherries, plums, blueberries and more — go dormant in the fall and need a certain amount of winter chill before they can wake up properly and bloom with full potential. Chill accumulation isn’t about keeping trees cold for its own sake — it’s about meeting each cultivar’s winter requirement so it can bloom strong in spring.
When a tree receives enough chill, it transitions from deep dormancy into “spring readiness.” If the requirement is not met, growers often see weak or scattered bloom, delayed leaf-out, poor fruit set, and an overall lighter crop. When chill requirements are fully met before warm weather arrives, bloom is more synchronized, pollination improves, and the orchard gets its best possible start to the season.
Different models describe the same underlying process in different ways:
There is no single best model for every region, which is why GetChill computes all three every time and lets you focus on the one that matches your experience.
Chill accumulation alone doesn’t set bloom date, but it explains a lot about timing and crop behavior. When combined with phenology notes and growing degree days, it becomes a powerful tool for pruning, thinning, labor planning, and frost-risk awareness.