Mohn says the last thing to consider is chill hours — the time the tree must spend between 32 and 45 degrees Fahrenheit to flower and fruit properly. (Maps outlining the chill hours across the United States are available online.) Think of the number of chill hours as an alarm clock for the tree; once it hits its required number, the tree will wake up, no matter what’s happening with Mother Nature. For example, if the tree requires a low number of chill hours, but winters are long and cold, it will bloom before spring arrives, the blooms will fall off, and the tree won’t fruit properly in the spring. Conversely, if a tree requires too many chill hours for the climate, it will bloom too late in the year to fruit correctly.
