Floral Morphology Differs Among New Northern Highbush Blueberry Cultivars

Variation in floral morphology and timing of bloom are common among cultivars of northern highbush blueberry (Vaccinium corymbosum L.). These differences can affect the ability of commercial pollinators to effectively pollinate and fertilize ovules, which can impact fruit set, berry size, and ultimate yields. New northern highbush blueberry cultivars may exhibit differences in flower morphology, which could impact pollination and fruit set. Evaluation of new cultivars compared to standard industry cultivars is of specific importance in predicting potential pollination constraints by a honey bee (Apis mellifera), one of the primary pollinators in North America, and in developing optimal hive stocking densities. Three new cultivars (‘Blue Ribbon’, ‘Top Shelf’, and ‘Cargo’) were compared to an industry standard (‘Duke’) for floral morphology and relative bloom phenology. All new cultivars had significantly smaller flowers as compared to ‘Duke’; however, ‘Top Shelf’ flowers exhibited a unique characteristic whereby many flowers (81%) had partially fused petals. Reduced flower size of new cultivars suggests floral morphology may be a constraint to effective pollination by honey bees and/or these cultivars will require higher honey bee stocking densities for effective pollination. However, the partially unfused petals in ‘Top Shelf’ may provide improved exposure to the stamen and pistil, which could increase accessibility to pollinators like the honey bee and promote pollination and fruit set.