Chilling Requirements in Chill Portions for California Crops

Part 3 in the series - What can we learn from the low chill winter of 2013-2014 In my last post, Counting Chill Better – Using the Chill Portions Model, I discussed how the chill portions model (also known as the Dynamic Model) is different from the chill hours model. Now that you can figure out how much chill you got in chill portions, how much do you need? Below is a table of the estimated chilling requirements of most of California’s major tree crops, and a few particular important cultivars. Most of the requirements listed below are based on scientific research. A few (*) are estimates based on how much chill we got last winter and how the crops responded in the spring and at harvest. If you are interested in the requirements of cultivars not listed here (especially for apricots, cherries, peaches and nectarines) or want to know the scientific reference information for a particular estimate, check out the more thorough version of this list at the UC Davis Fruit & Nut Center site.

Crop	Chill Portions Requirement
Almonds	22-32
‘Nonpareil’	23
Apples (‘Golden Delicious’)	50
Apricots	30-69
Cherry	30-70
‘Brooks’	37
Nectarines	12-42
Peaches	8-75
Pistachios	54-65
‘Kerman’*	54-58
‘Peters’*	60-65
Prune (‘Improved French’)*	55-60
Walnut	38-72
‘Chandler’*	45-50