Fruit Development Period of Several Southern Highbush Blueberry Cultivars

Flowering and ripening times were recorded for the southern highbush blueberry (Vaccinium corymbosum) cultivars Emerald, O'Neal, and Star, along with the newer University of Georgia releases 'Camellia', 'Rebel', 'Southern Splendour', and 'Suziblue' over several years at three locations in Georgia. Nearby weather stations were utilized to record temperatures for calculating chill hours and heat units during each of the years. These data were used to calculate fruit development period for the different cultivars as a function of real time (days) and thermal time (heat units). Depending on cultivar and chill hours at a location, flowering time varied as much as 29 days from year to year. Overall, 'Emerald' was the earliest flowering, followed by 'Rebel'. 'Camellia' was the latest to flower among the cultivars. Average fruit development period for the cultivars were: Southern Splendour, 56.2 days; Rebel, 65.3 days; Suziblue, 65.5 days; Star, 67.1 days; Camellia, 68.8 days; O'Neal, 71.9 days; and Emerald, 82.8 days. The shortened fruit development period of 'Southern Splendour' resulted in a ripening time similar to 'Rebel' and 'Star', even though flowering time of 'Southern Splendour' was often several days later. Using heat units instead of days did not greatly reduce the coefficient of variation associated with fruit development period. However, the mean absolute and maximum difference between observed and predicted time to ripening was improved for most cultivars when heat units were used. These data should be useful in estimating how these blueberry cultivars will perform under diverse environments.