Dancing Bee Apiary
"Dancing Bees and Fruitful Trees"
Hardiness Zones and Chill Hours
PLANT HARDINESS ZONES
The USDA has updated their Plant
Hardiness Map that divides the nation
into regions based on average minimum
temperatures. These are not absolute
minimums, but average annual
temperatures. These Zones are used to
describe the range in which plants are
adapted to and can be grown. We list
these Zones for each of our products.  
Dark Purple is Zone 4, Blue Zone 5,
Dark Green Zone 6, Pale Green Zone 7,
Yellow Zone 8 and Tan Zone 9. Our
nursery is located in Zone 8a. Inside
these Zones, variation in elevation, site
location, directional orientation and
proximity to bodies of water such as
lakes or oceans can create variation in
temperature that can raise or lower the
temperatures experienced at the site.
These microclimates can allow or prohibit the planting of particular plants. For instance, cold hardy citrus can be grown
along the coast or on islands even as far north as South Carolina, where the effect of the warmer ocean keeps the air
temperature from getting as cold as even a few miles inland. Trees that break dormancy early may likewise be damaged by
late season frosts that settle in frost pockets at the bottom of valleys or even swales, whereas higher on hillsides the cold air
drains off down to the bottom and does not damage the trees. The south side of a house can be much warmer with winter
sun and protection from cold north winter winds. The mass of the house emanates heat at night, allowing planting of cold
sensitive plants close to the building. Similarly, temperatures in cities are often much warmer than surrounding countryside,
where asphalt and buildings store heat. Consideration of microclimate is very important in choosing what to plant.

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.