2019 ASHS Annual Conference

Landscape plants that attract pollinators are becoming more popular as concerns over pollinator health resonate with consumers. Asclepias is an important ecologic host and food source for many butterfly species that utilize nectar and foliage as food sources. It is also known for its attractive floral structures and performance in landscape environments with minimal fertilizer and irrigation inputs. Despite having ornamental and ecologically valuable traits, cultivars of Asclepias spp. are not commonly found in the ornamental market as Asclepias spp. does not tolerate commercial growing protocols that incorporate high fertility and irrigation rates, and as a result grow to heights too large for efficient racking and shipping or suffer from pathogens. This study utilized nine species of Asclepias as pollen donors, hybridized with Asclepias tuberosa (maternal parent), with the goal of obtaining hybrid progeny with improved phenotypic characteristics and environmental tolerances. Pollen parents included A. speciosa Torr., A. syriaca L., A. viridis Walter, A. incarnata L., A. purpurascens L., A. hirtella Woodson, A. verticillata L., A. curassavica L and A. fascicularis Decne. Yet before attempting to make crosses, controlled pollination techniques needed to be developed, as none were available for Asclepias and success is extremely low (>1%) in nature. A method developed in this study inverted Asclepias pollinia when making crosses, to optimize contact with the stigmatic surface. Results showed a twelve-fold increase in seed pod (fruit) set (from >1% observed in nature to 11.72%). By using the pollination method developed in this study, successful hybrids were created between A. tuberosa and four of the nine species that served as pollen parents. Germination techniques of direct seeding and 30-day cold-moist stratification were also tested when assessing viability of hybrid seed. Hybrid crosses had germination percentages comparable or greater than that of selfed A. tuberosa (the maternal parent) when using both seed treatments; however cold moist stratification resulted in higher germination rates. Inheritance of key phenotypic traits will be evaluated, and this information will provide the industry an avenue to increase production and distribution of Asclepias to the market.