What Causes Blueberries to Bloom Early?

Q: Every spring I find myself rushing out to put Christmas lights and blankets over my blueberry blooms to avoid them being damaged by a late winter freeze. What causes blueberries to bloom so early? 

A: Blueberries are triggered to bloom based on the number of chill hours required by a particular plant during the winter. Different species or varieties of blueberries require different amounts of cold weather to bloom. Cold damage depends on the stage of development of a blueberry flower. During the winter, dormant flower buds of highbush blueberries will survive temperatures as low as -20°F while rabbiteye blueberries are often damaged below 0°F. By the time individual flowers begin to protrude from the bud, temperatures below 20°F will damage the most exposed flowers. When flowers are fully open, temperatures below 26°F will kill them.

Summary? Blueberries that require lots of chill hours are less likely to be hurt by a late spring freeze. University of Georgia blueberry specialist Dr. Scott Nesmith says the Southern highbush ‘Camellia’ is pretty safe to plant, as are the new ‘Miss Jackie’, ‘Miss Lilly’ and ‘Miss Alice Mae’. Good rabbiteye varieties include ‘Baldwin’, ‘Alapaha’, ‘Ochlockonee’, and ‘Titan’.