Final report for FNE18-905
Project Information
This project aimed to explore the potential of planting Japanese American hybrid plums in high density plantings similar to those systems now commonly used with apples. The idea was to first test five varieties (Waneta, Lacrescent, Superior, Toka, and Alderman) of hybrid plums all using the vertical axis system. Secondly, one variety would compare the efficiency of using bi-axis, quad-v, and vertical axis system with just one variety-- Superior. The two parts of the project were designed to test which systems produced the most qualities plums per acre and per year.
The first major obstacle was obtaining trees. An underutilized fruit, hybrid plums proved largely unavailable, partially because at least two nurseries that specialized in these trees had recently gone out of business. We solved this by using our own rootstock and scionwood and grafting our own trees, as we have done before. The trees grafted with an acceptable success rate and began growing. Unfortunately, the following three growing seasons were ones of severe, record-breaking drought. Despite our best efforts, too many of the trees either died or grew so slowly that realistically comparing the different varieties and high density systems was impossible.
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.
Cooperators
- - Technical Advisor
Research
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 were 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 were intended to be trained according to the vertical axis system. They woul 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 was recorded to establish the initial cost of each of the five plantings. The cost of the trees plus the cost of labor was recorded.
Ten trees in part two were intended to be trained in vertical axis (at a spacing of seven feet), as above. The closer spacing was to 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 were 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 were 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 had significant root systems and were established in the field. All trees in part one were still under two feet tall. We anticipated 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 2020 growing season, we requested an extension of a year for this project. Trees were maintained during the growing season but little tree growth occurred.
2021 proved to be another year of severe drought in northern Maine. Because of the location of the orchard and the number of trees it was impractical to irrigate. Weak trees that had died during the winter were replanted with extras from the grafts we had done in 2018. We mulched the trees appropriately and weeded the orchard but survivability and growth proved too poor to achieve measurable results.
The main change that first 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.
Drought continued in 2021 in northern Maine. As a result, the trees for this project did not thrive. In fact 60% of the trees died during the summer. The ones that did survive grew a meager amount. Because of the severe climate stress on these trees it was impossible to compare the different training systems for high density plums. Although high density plums may still be a viable production method of fruit production, severe weather prevented us from evaluating.
We were able to evaluate the cost of planting and maintaining a plum orchard. Purchased hybrid plums currently go for roughly $30/tree. An orchard of 80 trees would cost roughly $2400, though the cost would be much less if trees were grafted on farm. Maintaining the trees took 60 hours each year-- mulching, weeding, and replanting as necessary. We did not have to do much pruning because of poor growth but the time not spent on that was spent on replanting so the figure of 60 hours per year to tend 80 plum trees should hold up. At $20/hour, maintenance of a plum orchard of this size would cost roughly $2400 in labor per year. With the price of fruit on the rise, this figure indicates that in better weather conditions, plums may be an economically viable crop.
Although it is hard to definitively determine the cause of four years of drought, this project seems to indicate that the climate is becoming more erratic and some crops may be more difficult to establish than in years past.
This project aimed to explore the potential of planting Japanese American hybrid plums in high density plantings similar to those systems now commonly used with apples. The idea was to first test five varieties (Waneta, Lacrescent, Superior, Toka, and Alderman) of hybrid plums all using the vertical axis system. Secondly, one variety would compare the efficiency of using bi-axis, quad-v, and vertical axis system with just one variety-- Superior. The two parts of the project were designed to test which systems produced the most qualities plums per acre and per year.
The first major obstacle was obtaining trees. An underutilized fruit, hybrid plums proved largely unavailable, partially because at least two nurseries that specialized in these trees had recently gone out of business. We solved this by using our own rootstock and scionwood and grafting our own trees, as we have done before. The trees grafted with an acceptable success rate and began growing. Unfortunately, the following three growing seasons were ones of severe, record-breaking drought. Despite our best efforts, too many of the trees either died or grew so slowly that realistically comparing the different varieties and high density systems was impossible.
Education & Outreach Activities and Participation Summary
Participation Summary:
Outreach was unable to be completed because of severe weather conditions affecting the growth of plants.
Learning Outcomes
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.
Project Outcomes
This project has inspired me to work more with my advisor, Renae Moran, to establish and test roostocks for Japanese-American hybrid plums.