What are Chill Hours & Why Are They Important?
Your fruit trees need to "Chill Out" - What Are Chill Hours and Why Do Fruit and Nut Trees Need Them?
Nut and fruit trees, except citrus, require a specific number of chill hours each winter to regulate their growth.
What Are Chill Hours?
Chill hours are the period when the temperature remains between 32°-45°F, signaling to trees that winter has arrived. This process breaks down the hormone responsible for dormancy, enabling buds to develop into flowers or foliage as the weather warms up in late winter.
Important to note: Temperatures below 32°F do not count toward chill hours, and hours above 60°F can subtract from the total accumulated chill hours.
Why Do Chill Hours Matter?
If a tree does not receive enough chill hours during winter, it may experience:
- Buds that fail to open or open unevenly
- Reduced or misshapen fruit production
Chill Hour Requirements for Different Trees
The number of chill hours required varies between species:
- Lowest requirements: Figs, olives, quince
- Moderate requirements: Persimmons, pomegranates, almonds, chestnuts
- Highest requirements: Cherries, apples, peaches, plums
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