|Hardiness Zones and Chill Hours
Many deciduous trees (trees that lose their leaves in winter), such as apples, peaches, pears, plums, flowering cherries and
dogwoods, require a period of dormancy and the accumulation of chilling to produce flowers and fruit. A chill hour is the
amount of chilling received by a plant at 45 degrees F. The chilling requirement is the total number of hours required during the
winter for a particular cultivar to induce the tree to break dormancy and produce flowers.
Regions vary greatly in the amount of chilling they receive. For example, some varieties of fruit trees require 1,000 hours of
chilling before breaking dormancy, while others only require 200 hours of chilling to be able to bear fruit. A tree that needs
1,000 hours will not bear fruit or grow in areas with lower chill hours.
A tree with low chill hours may grow farther north, but it may bloom too early in the season (because its chilling requirement
has been met with just a few cold fronts) and later freezes may damage flowers or fruit. It is very important to know what
chilling hours you receive to make sure you plant the correct varieties for your location.
Chilling hours also vary year to year, depending on the amount of cold fronts each winter. A region that averages 500 Chill
hours per year might receive only 350 hours in a warm winter, but 800 in a cold winter. Therefore, it is good to plant several
different cultivars with a range of chilling requirements. Keep in mind that you don't want to plant a variety with a requirement
for 800 hours if your average is only 250.
As previously mentioned, our nursery is located in zone 8a and zone 8a has 700+ chill hours depending on the serverity of the
weather which lately can vary greatly fron year to year season to season. We have been known to have up to 2400 chill hours
in a season! We have worked hard over the years and through trial and error have been able to determine which varieties of
trees thrive in our adverse climate.