Graduate Research Assistant Tennessee State University Hillsboro, Tennessee
Body of Abstract: Hydrangea macrophylla, bigleaf hydrangea, is a popular ornamental shrub worldwide for landscapes, potted plants, and cut flowers. A major aesthetic focus of bigleaf hydrangea are their large, colorful inflorescences. Because the inflorescence is one of the most desired traits of bigleaf hydrangea, plants that are able to rebloom throughout the growing season are desired. For this study, 41 different cultivars marketed as reblooming were evaluated for flowering performance across two growing seasons. Inflorescences were counted every two weeks from June 4th 2021, to October 20th 2021 and June 6th 2022 to October 19th 2022. The area under inflorescence development curve was calculated. During the first growing season, ‘Oakhill’ had the highest rate of inflorescence progress while ‘Lady in Red’ had the lowest progress. At the final observation date, ‘David Ramsey’ and ‘Oakhill’ had the highest number of inflorescences on the plants, with an average of seven, and ‘Lady in Red’, ‘Blauer Prinz’, ‘Everlasting Revolution’, ‘Let’s Dance Starlight’, and ‘Forever and Ever Together’ had no inflorescences present at the final observation date. During the second growing season, ‘Let’s Dance Rhythmic Blue’ had the highest rate of inflorescence progress and ‘Blushing Bride’ had the lowest progress. By the final observation, a majority of the plants had no inflorescences. ‘Twist-n-Shout, ‘Princess Diana’, and ‘Oakhill’ were the only plants to have any inflorescences by the last observation. This study showed that reblooming bigleaf hydrangeas rebloom at different numbers across a growing season and will supplement future studies in establishing reblooming mechanisms of bigleaf hydrangea cultivars.