Chill Hours Calculator
Calculate chill hours for fruit trees to ensure proper dormancy and flowering. Use standard, Utah, or dynamic models.
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Track Winter Chill for Fruit Trees
Chill hours are the accumulated hours of cold temperatures (typically 32-45°F) that deciduous fruit trees and perennial plants need during winter dormancy. Proper chill accumulation is essential for healthy bud break, flowering, and fruit production in spring.
What Are Chill Hours?
Chill hours represent the time trees spend within a specific cold temperature range during dormancy. This cold exposure triggers hormonal changes that allow trees to break dormancy and produce fruit. Different fruit varieties have different chill hour requirements, making location and variety selection critical for successful orchards.
Standard Chill Hours Formula
CH = Σ hours where 32°F ≤ T ≤ 45°FWhy Track Chill Hours?
Variety Selection
Choose fruit tree varieties suited to your region's typical chill accumulation.
Predict Bloom Time
Estimate when trees will break dormancy and begin flowering.
Manage Risk
Identify years with insufficient chill that may affect fruit production.
How to Calculate Chill Hours
Common Applications
Apple Orchards
Most apple varieties need 800-1200 chill hours for proper fruiting.
Stone Fruits
Peaches, cherries, and plums have varying chill requirements (300-1000 hours).
Climate Assessment
Evaluate locations for new orchard establishment.
Season Planning
Monitor winter progress and predict spring growth timing.
Frequently Asked Questions
Trees may experience delayed or irregular bud break, reduced fruit set, poor fruit quality, and extended bloom periods that increase frost damage risk.