Effect of Timing and Severity of Summer Pruning on Vegetative and Reproductive Traits of Southern Highbush Blueberry

Summer pruning is a major practice for blueberry management, but research-based recommendations are lacking in the southeastern U.S. The objective of this study is to determine the effects of timing and severity of summer pruning on vegetative and reproductive growth in ‘Jewel’ and ‘Emerald’ southern highbush blueberry. Mature plants of both cultivars were subjected to the following treatments for three years: 1) control – no pruning; 2) control – detailed hand pruning; 3) pruning 30% of existing foliage in early June (30% June); 4) pruning 30% of existing foliage in mid-July (30% July); 5) pruning 30% of existing foliage in early June followed by shoot tipping in mid-July (30% June+tip); and 6) pruning 60% of existing foliage in early June, followed by shoot tipping in mid-July (60% June+tip). Regrowth volume of the non-pruned plants decreased significantly from the first to third year in ‘Jewel’, while regrowth in the other treatments either increased or was similar between years. In ‘Emerald’, there was also a trend towards reduction of regrowth volume in the non-pruned control (P=0.058). Flower bud number per shoot decreased in non-pruned plants of both cultivars. In ‘Jewel’, hand-pruned and 30% July also showed this reduction in number of flower buds per shoot. Total flower bud number per plant was not affected by treatments in ‘Emerald’; however, in ‘Jewel’ total flower buds per plant decreased in non-pruned plants from 2012 to 2013. There were no effects of pruning on yield or yield distribution during the season in ‘Emerald’. However, 60% June+tip increased the average berry weight early in the season compared to non-pruned and 30% July treatments. In ‘Jewel’, yield was greater in 30% June+tip compared to non-pruned, hand-pruned and 60% June+tip treatments. The 60% June+tip treatment also shifted the highest yielding period from late April to early and late May in 2013, a trend that was also observed in 2012. Late pruning (30% July) did not reduce or shift yield in either cultivar. Data indicate that summer pruning, regardless of timing or severity, is beneficial for vegetative growth in both cultivars. There was no pronounced effect of pruning treatments on reproductive traits for ‘Emerald’. For ‘Jewel’, early moderate pruning followed by tipping promoted high, early yields with large berries.