ASHS 2024 Conference

Deciduous azaleas (Rhododendron spp.) are native to the Eastern United States and have potential for increased adoption in the ornamental nursery and landscape market. However, plant availability is currently limited and trials on the growth and performance of each species are lacking. Furthermore, seed propagation is the common production method for native azaleas, which can result in phenotypic variation and a longer period of time to produce a saleable product, relative to vegetative propagation. Under optimum growing conditions, native azaleas can be low-input plants with minimal insect and disease issues. However, they can also be susceptible to summer heat stress and require well-drained soils and partial-shade similar to their indigenous growing environments in order to thrive. To determine which species may be most well-adapted to typical container nursery production practices, container trials were established to evaluate nine different species of native azaleas, including R. arborescens, R. atlanticum, R. austrinum, R. canescens, R. cumberlandense, R. flammeum, R. periclymenoides, R. prunifolium, and R. vaseyi, grown in both full sun and 50% shade conditions. Seed-grown one-year old liners of each of the nine different species were established in one-gallon containers and evaluated for growth rate and physiological characteristics, such as leaf chlorophyll content and normalized difference vegetation index (NDVI), comparing plants grown in full sun vs. 50% shade. In year two, bloom dates and number of blooms per plant in full sun vs. 50% shade were compared. R. atlanticum demonstrated the greatest potential for commercial production, especially when grown under 50% shade conditions, based on growth rate and average number of blooms per plant. These results suggest that R. atlanticum may be a reliable species of native azalea for growers to commercially produce for this growing market segment, while other species may still have potential, albeit with additional attention to their specific production requirements.