Jump Starting New Pawpaw Variety Production for the Industry: Developing Grafting and Top Working Approaches for Growers

Pawpaw, a tree fruit native to the Eastern U.S., is in small-scale commercial production with its popularity on the rise. Pawpaw fruit have fresh market appeal for farmers’ markets and Community Supported Agriculture (CSAs), and processing appeal for frozen pulp production for sale to gourmet restaurants. There are over 100 limited resource farmers in Kentucky alone who have small plantings of seedling pawpaw trees or wild trees that with grafting and top working could serve as rootstock and enable rapid production from grafts of high quality and high demand pawpaw fruit. The objective of this study was to develop methods to optimize grafting or budding success by cultivar and grafting time on pawpaw seedling rootstock trees. Six 17-year-old seedling trees were selected at the KSU Harold R. Benson Research and Demonstration Farm, and branches were topworked with the pawpaw selections KSU Atwood, Hi1-4, Hi4-1, and Hi7-5 via bark inlay grafting in late May 2015. Additionally, thirty-five 4-year-old rootstock trees were topworked, by chip budding or whip and tongue, with the pawpaw selections KSU-Atwood, Hi1-4, Hi4-1, and Hi7-5 on two dates, late-May and mid-June 2015. Chip budding was performed in May with dormant buds collected in March 2015. Whip and tongue grafts were performed in June with new green growth collected one day prior to grafting. None of the bark inlay grafts performed on older trees successfully formed graft unions. From this preliminary experiment, this method does not appear to be a feasible method for topworking pawpaw trees. Using earlier grafting dates and smaller branches may improve grafting success in the future. For chip budded trees, 44% of 4-year-old rootstock trees chip budded in May successfully formed graft unions. For the whip and tongue grafted trees, 41% of trees formed successful graft unions. Trees grafted with green wood showed more growth during the 2015 growing season. Trees chip budded with dormant wood healed; however, these buds showed little to no growth during the 2015 growing season. These grafts and buds will continue to be evaluated in 2016. Either of these grafting methods show promise for topworking smaller diameter pawpaw trees.