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Late spring frosts are a major concern to blueberry growers in the southeastern United States. Cold hardiness of flower buds (stages 4 to 6) was evaluated in three southern highbush blueberry cultivars (`Cooper', `O'Neal', and `Gulfcoast'). Differential thermal analysis (DTA) and tissue browning tests revealed that the critical temperature and ovary damage occurred at –11C in `Cooper', –12C in `O'Neal', and –13C in `Gulfcoast'.
Cold acclimation of `Tifblue' rabbiteye blueberry was determined using differential thermal analysis (DTA). Electrolyte leakage and tissue browning test results were correlated with DTA. DTA showed that three exotherms occurred: exotherm 1 (ET) associated with extracellular freezing, exotherm 2 (CT) associated with tissue injury, and exotherm 3 (LTE) not associated with tissue injury. Maximum hardiness (–20C) occurred in January. The LT50 measured by electrolyte leakage and tissue browning was about –17C and –15C, respectively. Acclimation began in November and deacclimation in mid-Feb. 1994.