Many plants become dormant during the cool season. If the cool season is not cool enough for a long enough period, many fruit-producing plants have a difficult time knowing when to overcome dormancy. Like growing degree-day units that are used to track temperature differences over a certain threshold over a period of time, chilling hours offer a way to track length of exposure to optimum dormancy temperatures. Maps of accumulated and chilling hours and chilling hours departure have been developed for growers to monitor the number of chilling hours over a dormant season based upon popular chilling temperature ranges. For more information, see our "About Chilling Hours Product" page.

Almond	500-600		Mulberry	400
Apple	400-1000 (low-chill varieties are less)		Peach	600-800
Apricot	500-600		Pear, European	600-800
Blackberry	200-500		Pear, Japanese	400-500
Blueberry, Northern	800		Persimmon	200-400
Cherry	700-800		Plum Cot	400
Chestnut	400-500		Plum, European	800-900
Citrus	0		Plum, Japanese	300-500
Currant	800-1000		Pomegranate	100-200
Fig	100-200		Quince	300-500
Filbert	800		Raspberries	700-800
Gooseberry	800-1000		Strawberry	200-300
Grape	100+		Walnut	600-700
Kiwi	600-800