Submitted to: Journal of American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2007
Publication Date: 1/1/2008
Citation: Thomas, A.L., Brauer, D.K., Sauer, T.J., Coggeshall, M.V., Ellersieck, M.R. 2008. Cultivar influences rootstock and scion survival of grafted black walnut. Journal of American Pomological Society. 62(1):3-12. Interpretive Summary: There is growing interest among landowners in the United States in conservation and agroforestry practices in which eastern black walnuts grown for nut production are a component. Management practices for nut production for this tree are poorly developed. ARS scientists from Booneville AR and Ames Iowa and cooperating scientists from the University of Missouri compared the survival and growth of grafted walnut trees with differing rootstocks at four different locations in Arkansas and Missouri. Grafted trees with rootstocks from the variety Kwik Krop were more likely to be alive three years after transplanting than grafted trees with rootstock from the either Thomas or Sparrow variety. Landowners planting eastern black walnuts for nut production will interested in these results because they identify a management option that promotes seedling tree establishment. Nursery producers who produce grafted seedling trees will be interested in these results also.
Technical Abstract: Black walnut (Juglans nigra L.) is being increasingly planted and cultivated in the Midwest, USA for the economic potential of both its wood and nuts. Trees that are principally established for nut production have greater potential for long-term productivity and profit if they are grafted to superior nut-producing cultivars. While numerous productive cultivars have been identified that perform well as scions, advances have not yet been made toward developing superior black walnut rootstocks. Furthermore, very little is known about how various scion or rootstock cultivars may interact with each other and their environment. The objective of this study, therefore, was to evaluate early transplant performance of large numbers of various scion -rootstock combinations across four disparate locations, and to determine which cultivars or cultivar graft combinations may be best for successful establishment of new plantings. Twenty different scion - rootstock combinations of grafted black walnut trees were transplanted at four Missouri / Arkansas locations in Fall 1999 and Spring 2001. All trees were pre-grafted, consisting of potted two-year-old seedling rootstocks from known female parentage (open-pollinated seeds from named cultivars), and one-year-old scions of superior nut-producing cultivars. Rootstock and scion survival at all sites was assessed in Fall 2002. Seedlings from the cultivar Kwik-Krop exhibited superior rootstock survival (78%) compared with Sparrow (55%), Thomas (58%), and an unimproved nursery bedrun rootstock (63%), but Kwik-Krop rootstock but did not interact with or influence scion cultivar survival. Among trees with surviving rootstocks, Kwik-Krop scions also survived better (96%) than Surprise (77%) or Emma K (78%) scions. Over the entire range of rootstocks, Thomas scions improved rootstock survival (77%) compared with Sparrow (62%), Kwik-Krop (60%), and Surprise (54%) scions. These results suggest that both scion and rootstock seedling cultivar selection can be an important consideration for successful establishment of grafted black walnut plantings.