Shooting Forward: Optimizing Establishment and Early Grafting Success for Pawpaw Growers

Commodities

Practices

Pawpaw (Asimina triloba), a native North American tree fruit, is gaining popularity in small-scale commercial production for both fresh-market sales and processed pulp. Many small farmers are interested in establishing orchards of newly available commercial pawpaw varieties with high yield, excellent fruit quality, and increased consumer demand for fruit. However, high costs of grafted trees ($30-$100 per plant) and poor field establishment rates have limited expansion of the pawpaw industry, particularly among small farmers. In Kentucky, more than 100 small farmers already cultivate pawpaw, yet many report mortality rates exceeding 30-50% within two years of planting due to transplant shock, root damage, and poor acclimation from shade to full sun, and failure to meet optimal fertilization requirements. Purchasing less expensive seedling rootstock trees (approximately $20 each) and subsequently top-working these with non-patented, superior cultivars could reduce initial costs. However, whether a grower plants grafted or seedling trees, high first-year mortality and poor vigor continue to represent significant economic challenges. Root applied biostimulants to stressed trees has shown promise for improving tree survival. This project seeks to improve pawpaw tree establishment and reduce input costs through optimized fertility and root enhancement strategies.

Establishment of seedling rootstock in orchards followed by top-working with scionwood of superior pawpaw varieties could also reduce the cost of establishing orchards with high-quality grafted varieties, helping small farms economically to be able to start pawpaw orchards. The objectives of this proposal are to: 1) Determine the impact of fertilization type (none, urea applied once in the spring, or monthly fertigation in May, June, July and August) and root biostimulants (none, Stimplex®, RootXCell®, and Stimplex + RootXCell®) on the establishment, early growth, and grafting success of newly planted pawpaw orchards at Kentucky State University, University of Kentucky, and Morehead State University; 2) Examine orchard establishment with or without biostimulant treatments and fertilization type (from Objective 1) through multi-location field trials at four grower sites; followed by the evaluation of grafting success rates of different cultivars (slow and vigorous scions); 3) Conduct an economic analysis of the cost of inputs for orchard establishment compared to current practices; and 4) Produce Extension bulletins and YouTube videos detailing optimal establishment and grafting workshops for growers and stakeholders. Foliar analysis and soil sample nutrient content will be taken in experiments in objective 1 and 2 to determine the impact of biostimulants on nutrient uptake of trees. This integrated research and outreach project will generate science-based recommendations for improving pawpaw orchard survival, growth, and grafting success, lowering establishment costs and supporting small growers in developing profitable, sustainable pawpaw production systems.

1) Determine the impact of fertilization type (none, urea applied once in the spring, or fertigation applied monthly in May, June, July, and August) and root biostimulants (none, Stimplex®, RootXCell®, and Stimplex + RootXCell®) on the establishment, early growth, and grafting success of newly planted pawpaw orchards at Kentucky State University, University of Kentucky, and Morehead State University;

2) Examine orchard establishment with or without biostimulant treatments and fertilization type (from Objective 1) through multi-location field trials at four grower sites; followed by the evaluation of grafting success rates of different cultivars (slow and vigorous scions);

3) Conduct an economic analysis of the cost of inputs for orchard establishment compared to current practices; and

4) Produce Extension bulletins and YouTube videos detailing optimal establishment and grafting workshops for growers and stakeholders.