Anthony Bratsch,1 Robert Bellm,2 and Don Kniepkamp3
ADDITIONAL INDEX WORDS. Asimina triloba, rootstock, anthesis, native, scaffold, axillary
SUMMARY. Following spring planting in 1998, and for four seasons (1998–2001), early growth and development were characterized for seven grafted [PawPaw Foundation (PPF), Frankfort, Ky.) pawpaw Regional variety trial (PRVT) rootstock] pawpaw (Asimina triloba) varieties, ‘Davis’, ‘Taylor’, ‘Rebecca’s Gold’, ‘Sunflower’, ‘Overleese’, ‘Prolific’, ‘Wells’, and one nongrafted seedling strain. Survival rate after four seasons was 96.5% for grafted trees and 100% for seedling trees. Entries exhibited significant differences in total height, trunk cross-sectional area (TCSA), average shoot length, first winter cold injury and percent bloom. By the end of 2000, seedling tree height and TCSA were greater as compared to the named varieties. Seedling height averaged 134 cm (52.8 inches), with a TCSA of 4.54 cm² (0.704 inch²), while the least vigorous variety (Davis) had an average height of 77 cm (30.3 inches) and a TCSA of 1.54 cm² (0.239 inch²). Average shoot length was significant only in the year of planting, ranging from 39.3 cm (15.47 inches) for ‘Davis’, to 61.3 cm (24.13 inches) for ‘Sunflower’. Tip dieback occurred in the winter following planting on all varieties; this damage ranged from 23.3% (“Taylor”) to 73.4% (“Overleese”). In 1999, lower axillary shoots (LSL) breaking below the damaged tips grew longer [31.1 to 50.6 cm (12.24 to 19.92 inches)] than upper distal axillary shoots (DASL) [15.8 to 44.6 cm (6.22 to 17.56 inches)], indicating a lack of apical dominance and vigor of emerging top buds. All named varieties developed flower buds by the spring of the fourth season, with budding ranging from an average of 0.5 buds/tree (“Rebecca Gold”) to 6.0 buds/tree (“Prolific”). Viability of these buds as determined by successful anthesis ranged from 0.4% (“Davis”) to 63.8% (“Wells”). No fruit were set from these flowers.
Pawpaw is the only temperate member of the tropical custard-apple family (Annonacea) (Bailey, 1960) and is the largest native fruit in North America (Darrow, 1975). It is endemic to the eastern U.S. and it grows in the wild as far north as Ontario, Canada, south to Florida, and west to Nebraska (Kral, 1960). It has received attention in recent years as a potential new crop with multiple uses, including fresh-market sales of the custard-like fruit, and the vegetative parts have medicinal and insecticidal properties (Layne, 1996). A PRVT was established at 12 locations across the United States, coordinated by staff at Kentucky State University, (KSU) Frankfort, Ky. (Pomper et al., 1999).
University of Illinois Extension, Edwardsville Extension Center, 200 University Park Dr., Edwardsville, IL 62025.
This project was developed to evaluate the potential of several alternative horticultural crops for southern Illinois growers. “Native Fruits and Nuts With Commercial Potential”, was initiated in 1997 and funded as a subgrant within the larger framework of a sustainable agriculture systems grant through the USDA Conservation 2000 program, written by the Illinois Department of Agriculture (IDOA SCCS and WC SA97-57). The horticulture portion of the project included evaluation of several species, and focused primarily on pecan (Carya illinoensis), black walnut (Juglans nigra) and pawpaw (Asimina triloba) variety evaluations. The authors would like to acknowledge and thank the staff of the Illinois Department of Agriculture, the St. Clair County Soil and Water Conservation District and others associated with the Henry White Farm Project. In addition we would like to express our appreciation to the members of the Illinois Nut Tree Growers Association and volunteers from the University of Illinois Master Gardener program, Madison/St. Clair County Extension Unit, as well as other interested enthusiasts who have been instrumental in their assistance in the maintenance and care of these experimental plots.
1Assistant professor. Current address: Department of Horticulture, 301 Saunders Hall, Virginia Tech, Blacksburg, VA 24061.
2Extension educator, crop systems.
3Master gardener, University of Illinois Extension, Madison/St. Clair Unit, #1 South Third Street Belleville, IL 62222.