Pruning Time × Cultivar Effects on Flower-bud Hardiness in Northern Highbush and Southern Highbush Blueberry

Abstract

A study was conducted to determine if early-fall pruning (vs. more typical winter pruning) of either northern highbush or southern highbush blueberries was detrimental to the development of optimum levels of mid-winter cold hardiness in floral buds under New Jersey conditions. Using a detached-shoot freeze-thaw assay, flower-bud LT50 values were determined in early January for both ‘Jersey’ (northern highbush) and ‘Legacy’ (southern highbush) blueberry bushes that had been subjected to early- or late-pruning protocols. Across 2 years, intrinsic differences due to genotype and genotype × year were present, but no significant differences due to pruning time were observed. The lack of pruning effects on flower-bud LT50 values suggests that cultivars with southern germplasm selected in areas such as North Carolina and further north may be treated similarly to northern highbush with respect to pruning time, including early-fall pruning.