Seasonal changes in the cold hardiness of the flower buds of highbush blueberry with varying species ancestry

Many blueberry cultivars contain genetic material from Vaccinium species adapted to southern and northern regions. In this study, we compared the flower bud hardiness of several cultivars with diverse species backgrounds during the fall, winter and spring. Twigs were collected from field-grown plants and frozen to a range of temperatures to determine the temperature resulting in 50% bud mortality. The hardiest cultivars were 'Sierra', 'Patriot' and 'Elliott', as well as the new cultivars 'Aurora' and 'Liberty'. 'Bluecrop' and 'Brigitta' were intermediate in hardiness, and 'Legacy' was the least hardy cultivar tested. Results suggest that hardiness of cultivars cannot be predicted accurately from their species composition.