In the first part of this project, five varieties of hybrid plums will be tested in the vertical axis high-density system to determine which variety does best with close spacing. Because plum trees are often more vigorous than dwarf trees of other species, finding the hybrid plum that does best in close spacing is a key element to making high-density hybrid plum plantings successful.
In general, finding the variety that performs well in a close spacing offers the most economic opportunity for an orchardist using the high-density method. The second part of the project will consist of testing three different high-density systems with one variety.
The objective of this part of the project is to determine if one of the three systems stands out as more efficient given the particular nature of hybrid plum trees.
Apple orchards and others have switched to high density systems in order to achieve economic and environmental viability. This project’s objectives aim to test high density systems for hybrid plums and thus offer more opportunity for the region’s orchardists.
This project is important in that it will help farmers in the northeast develop a potentially profitable crop. Japanese American hybrid plums are currently not being grown on a commercial scale. Identifying the best, most efficient methods to grow this crop while maximizing fruit production per acre could give fruit growers an important tool in maintaining economic and environmental sustainability. Using training methods and spacing techniques that have revolutionized the production of more common crops such as apples in recent decades, this project will help fruit growers — particular organic growers–survive in a competitive marketplace.
- - Technical Advisor
This project began in May of 2018. For part one, fifty trees were planted– ten of each variety(Waneta, Superior, Toka, LaCrescent, and Alderman)—five at a spacing of seven feet and five at a spacing of ten feet for each variety.
For part two, thirty trees will be planted—ten each in the vertical axis, bi axis, and quad v systems—originally the plan was to use variety Superior but because that variety was not available in large enough amounts even as scionwood, Alderman was used for part two.
The trees in part one will be trained according to the vertical axis system. They will be pruned as necessary, though pruning is usually kept to a minimum with high density systems in the first few years. Vertical axis systems allow for 300-600 trees per acre, depending on the spacing.
The labor involved in establishing each variety will be recorded to establish the initial cost of each of the five plantings. The cost of the trees plus the cost of labor will be recorded.
Ten trees in part two will be trained in vertical axis (at a spacing of seven feet), as above. The closer spacing will be used for this part of the project to better compare to bi-axis, and quad v, which typically involve close spacing.
Ten trees in part two will be planted using the bi-axis system, which involves establishing two leaders for the tree and planting at a spacing of three feet within the row. Bi-axis systems usually allow for planting 1200 trees per acre. Although bi-axis plantings can be difficult to establish, they allow for the possibility of high yields and are designed to maximize sunlight.
Ten trees in part two will also be planted using the quad-v system, which involves establishing four main scaffolds. Plantings at seven feet spacing in the row equal roughly 400 trees per acre. The quad v is easier to establish than some other high-density systems and allows for high yields but fruit size can be small.
In 2019, we were still working on establishing the trees for this project. Because plum trees of these varieties were initially unavailable in the numbers needed, we grafted trees ourselves at the beginning of the project. The trees now have significant root systems and are established in the field. All trees in part one are still under two feet tall. We anticipate proceeding with the research outlined above in 2020.
Because of disruption on the farm related to covid19 and because of severe drought in northern Maine for the entire growing season, we are requesting an extension of a year for this project. Trees were maintained during the growing season but little tree growth occurred.
The main change that occurred with this project was that we found that large trees of Japanese American hybrids were completely unavailable in the numbers needed for the project. We grafted trees for the project. This gave the advantage of having control over quality of trees but means that the project will take longer to achieve results. In 2018, we established the trees and cared for them as they got established for future research.
In Part One, trees all were in the 3-6″ range in height. Our plan is to measure them in the spring of 2019, prune them all to the same height, then proceed as outlined in our original proposal.
The trees in Part Two are all two year old trees six feet of height which we transplanted for this project. Training for them will begin in the spring of 2019.
This project is very much still a work in progress. Results will be measurable over the next two growing seasons. We are asking for an extension for this project because of covid 19 and severe drought throughout the growing season. Trees were maintained during 2020 but little growth occurred.
Education & Outreach Activities and Participation Summary
Outreach will be completed as the project progresses.
The extent to which this valuable fruit is not being studied or utilized became more apparent as the project got started. More research on these plums may lead to them being made more available for growers.
This project has inspired me to work more with my advisor, Renae Moran, to establish and test roostocks for Japanese-American hybrid plums.