Blueberries (Vaccinium spp.) are acidic soil-loving bushes that have been bred to fruit under a wide range of climatic conditions, from U.S. Department of Agriculture plant hardiness zone 3 to 9a, depending on species and cultivar. Traditionally, blueberries have been grown in cooler climates because the most common commercial bushes require many cold nights to fruit. However, both rabbiteye and Southern highbush varieties not only tolerate, but prefer, warmer conditions.
The term "chilling hours" refers to the amount of time a dormant plant needs for the production of growth-promoting hormones to overcome the growth-inhibiting hormones that caused its dormancy in the first place. While ambient temperatures between 35 and 55 degrees Fahrenheit will provide the cold hours necessary to trigger development of growth promoting hormones, 45 degrees is ideal. Chilling hours are only a guide, but they help gardeners determine which fruit-producing plants are best suited for their regions.
Southern highbush blueberries are the product of selective crossings between Northern highbush and Florida native blueberries, resulting in a medium-sized bush similar in fruiting and appearance to the traditional Northern highbush used for the bulk of commercial production. Southern highbush varieties only require 150 to 600 chilling hours to induce fruit production, unlike its Northern relatives that can require upward of 1,000 hours.
Southern Highbush Varieties
Southern highbush blueberries will often produce fruit without a pollinator, but you will get better fruit set if you grow more than one variety. The early season cultivars "O'Neal," "Sharpblue," "Misty" and "Star" are good producers in warm climates. "Legacy," "Jubilee" and "Southmoon" are mid-season choices. "Ozarkblue" is a late season cultivar that produces fruit just slightly ahead of rabbiteye blueberries.
Rabbiteye blueberries (V. ashei) are a species native to the Southeastern United States, where they evolved in a climate with hot summers and winters that are often mild. Unlike Southern highbush varieties, rabbiteye is a large, spreading bush, often reaching 15 feet tall and 10 feet wide. These bushes do not require pruning, but can be high maintenance while fruiting, since fruiting clusters may set over a much longer period of time than Southern highbush varieties. Rabbiteyes need 350 to 700 chilling hours.
Rabbiteye blueberries vary in their chilling hour requirements, but a few cultivars require less than 400 hours, including "Prince" (350 hours), "Woodard" (350 hours) and "Brightwell" (400 hours). Others require no more than 550 hours -- among those are "Climax" (450 hours), "Alapaha" (500 hours), "Austin" (500 hours), "Premier" (550 hours) and "Vernon" (550 hours).
- University of California Cooperative Extension: Growing Blueberries in the Sacramento Region
- University of California Cooperative Extension: Blueberry Research Launches Exciting New California Specialty Crop
- University of California Cooperative Extension: Blueberries
- Alabama Cooperative Extension System: Winter Chilling Requirements
- Texas A&M Agrilife Extension: Rabbiteye Blueberries
- University of Arkansas Cooperative Extension Service: Blueberry Production in the Home Garden
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