2019 ASHS Annual Conference

Trees account for the majority of expenses when establishing high-density plantings. Trees need to fill space rapidly and produce yields early in the life of the orchard to return the high investment costs. The vast proportion of nursery trees are harvested, stored, and shipped bare-root. These trees are prone to transplant-shock and require additional time to fill orchard space. The objective of this multi-year project is to determine whether root-pruning containers produce apple trees with higher quality root and shoot systems compared to field grown apple trees. We hypothesized that root-pruning containers would promote rapid canopy infill and expedite the return on investment of high-density plantings compared to bare-root trees.

The experiment was conducted in 2017 in two different sites the Michigan State University Horticulture Teaching and Research Center, and Sierra Gold nursery, Yuba City, CA. Three different apple cultivars ‘Gala’, ‘Fuji’, and ‘Honeycrisp’ were bench grafted to M9 ‘Nic29’ rootstock and divided into two production systems: Ellepot containers and field liners. Entire plants, including root systems, were carefully harvested from each production system throughout the growing season. Growth of Ellepot-produced trees was more uniform and total leaf area, average leaf size, and seasonal above-ground dry matter were higher than field grown trees, regardless of scion. Root morphology differed drastically between the two systems. Ellepot-produced trees had markedly higher fine root production and greater root length density compared to field liners. In spring 2018, container and bare-root trees were established in a new orchard using a RCB experimental design. Canopy and root development continued to be significantly greater for containerized trees than field liner/bare root trees throughout 2018 and by the end of the season, containerized trees accrued ~50% to 150% more growth. Roots also continued to show markedly greater fine root production. In subsequent years, flowering, fruiting and orchard productivity will be assessed and related to pre-plant factors to determine if these earlier advantages result in precocity.