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Winter Chill Hours for Fruit Trees

Beverly Hills Apple

Have you been wanting to plant a peach or apple tree in your back yard but thought you couldn’t grow them in Southern California? Well, you can! Many homeowners are growing apples, peaches, nectarines, plums and apricots in their yards. You do need to do your research on what varieties grow here and much of it is based on ‘chill hours.’ Huh? Like, chillin’ out with the fruit trees?  Not exactly…you see, these types of fruit trees, and some nut trees and even blueberries, need a certain number of ‘chill’ hours for them to bear fruit. There are different formulas for calculating chill hours but simply put, chill hours are defined as the hours that a fruit tree needs to be exposed to temperatures between 32-45°F to produce fruit.  That can be difficult here in Southern California. Luckily, those smart horticulturists have figured out a way to breed trees that don’t need thousands of chill hours to produce an apple like in Oregon and Washington. In these colder climates they can grow McIntosh apples with a 900 hour chill requirement or the Rome Beauty with 1000 hour chill requirement. In Southern California, we have the Anna Apple that only needs 100 hours or less to produce fruit! And customers have told us that sometimes they get 2 crops a year from these generous apple trees.

So how do the chill hours affect fruit production? During winter dormancy, typically November 1 – February 28/29, fruit trees have an interior mechanism that protects them from freezing to death. The first stage is the Chilling Requirement. The plant bud limits growth when temperatures are below 45°F. The second part of the dormant period is controlled by the temperature. Once the chilling requirement has been met, the tree then requires warmer temperatures to start growing in the spring. So you can see how in Southern California, with our varied winter temperatures, these fruit trees can get really confused by cold temperatures, then hot Santa Ana temps, followed by another cold spell, and so forth and so on. Buying fruit trees with a lower chill requirement will ensure more successful crops for your backyard orchard.
 
Here at Evergreen Nursery we carry the fruit trees that are successful in Southern California. If you live near the coast you will definitely want lower chill requirements for your trees than if you live inland in Escondido. For instance, Escondido averages 750 chill hours vs. La Jolla’s average of only 20 chill hours, although some microclimates in La Jolla have had success growing 'low chill' fruit. See the list below for the various trees we carry and their chill requirements:
 
Almonds
Variety Chill Hours
All-in-One 300-400
Mission 500
 
Apples
Variety Chill Hours
Anna 100
Beverly Hills 250
Cox Orange Pippin 700-800
Dorsett Golden 100-250
Ein Sheimer  100-300
Granny Smith 300-500
Fuji 300-400
Gala  500-700
Jonagold 700-800
Yellow Delicious 300-400
 
Apricots
Variety  Chill Hours
Blenheim 400-500
Gold Kist 300
Katy 200-300
 
Nectarines
Variety Chill Hours
Desert Delight 100-200
Fantasia 400-500
Goldmine 400
Panamint 250
Sunglo 850
 
Peaches
Variety Chill Hours
Babcock 200-300
Bonita 100-200
Bonanza 250
CA Curl-Free 200-300
Desert Gold 100-200
Donut/Peento 300
Early Elberta 800
Elberta 600
Florida Prince 100-150
May Pride 150-200
Red Haven 800
Rio Oso Gem 800
Santa Barbara 150-250
 
Pears
Variety Chill Hours
Comice 200-300
Hood 100-200
Kieffer 200-300
Pineapple 200
Seckel (Sugar) 500
 
Asian Pears
Variety Chill Hours
20th Century 300-400
Shinko 450
Shinseiki 250-300
 
Plums
Variety Chill Hours
Beauty 250
Burgundy 150-300
Green Gage 150-300
Mariposa 250
Methley 250
Santa Rosa 300
Satsuma 300
 
Persimmon
Fuyu - 200 Chill Hours
 
Pomegranate
Wonderful - 150 Chill Hours
 
Blueberry
Variety Chill Hours
Sunshine Blue 150
Sharpblue 150
Misty 200