2019 ASHS Annual Conference

The North American pawpaw (Asimina triloba) is a native tree fruit that is in small-scale commercial production across the Eastern United States. Fruit are sold in the fresh market as well as value-added products such as beer, wine, jam, and ice cream. Many farmers and landowners have seedling or wild pawpaw trees that produce small yields and low quality fruit. New commercially available pawpaw varieties are available with higher yields and fruit quality, and these wild and seedling trees could serve as rootstock to enable rapid production from grafts of superior cultivars. Bark inlay is a grafting technique which allows the use of a mature tree up to 8 cm diameter as rootstock. This technique has not been well developed for pawpaw and represents a method for growers to change over to improved cultivars. Seedling pawpaw trees take 7-9 years to produce fruit, whereas trees grafted using traditional methods onto small diameter (~1 cm) rootstock produce fruit in 3-4 years. Rapid growth from bark inlay grafting could shorten time to fruit production even further. Three commercially available pawpaw cultivars with large, high quality fruit and high yields were selected: ‘KSU-Atwood’, ‘Sunflower’, and ‘Susquehanna’. Three trees of each cultivar were grafted on two dates, early vs. late May at the Kentucky State University Research and Demonstration Farm in 2016, 2017, and 2018. Trees grafted using the bark inlay method in early May had a success rate of 78% in all three years, whereas trees grafted in late May had a success rate of 67% in 2016, 44% in 2017, and 33% in 2018. By year 2, trees grafted in early May had grown an average of 1.2 m compared to those grafted in late May growing 0.83 m. 57% of trees grafted in early May 2016 flowered in spring 2018, while 33% of trees grafted in late May 2016 flowered in 2018. 44% of trees grafted in early May 2016 produced fruit in 2018, 2 years earlier than would be expected with other grafting methods; while no trees grafted in late May 2016 fruited in 2018. Due to a higher success rate, improved growth, and more precocious flowering and fruiting, early May is preferable to late May for performing bark inlay grafting of pawpaw trees.