What are chill hours?

What are chill hours?

A deciduous tree is one that loses its leaves in winter (such as apples, peaches, plums, etc.).  Many deciduous fruit trees need a certain number of hours of low temperatures over the winter in order to grow back strongly in spring.  A chill hour is any hour under 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 & fruit.  In most of Maricopa County, we typically have around 400 chill hours (more or less depending on the type of winter we have).  Now, this doesn’t mean a tree with 500 chill hours won’t grow here.  In my own orchard, I’ve had a lot of success growing fruit trees with chill hour requirements up to 500-550.  It is important when buying deciduous fruit trees that you pay attention to the number of chill hours required for your area for each tree.  Keep in mind, a tree that needs 1,000 hours will likely not bear fruit in areas with lower chill hours like Maricopa County.  I won’t say a tree with 800+ hours, such as Bing cherries & Honeycrisp Apples, will never fruit here, however, it would be experimental & your money will be better spent on trees proven to fruit in our area.  That is what I take into consideration when selecting trees to sell at Flower of the Gods.