Washington State University researchers are studying a competitive cherry orchard system that trains upright fruiting offshoots, called UFOs, along horizontal leaders. Trees are planted at 35° to 40° angles. Heading cuts are avoided under this system.
Washington State University horticulturist Dr. Matt Whiting’s vision of a precocious, productive, and efficient orchard system that yields large, sweet cherries is now being tested throughout the Pacific Northwest in grower demonstration trials.
He envisions an efficient cherry orchard system as one that catches optimum sunlight radiation; maximizes the use of chemical sprays; minimizes management; utilizes the cherry tree’s natural growth habit; and readily incorporates technology. Moreover, the modern cherry orchard allows for the systematic treatment of the art of pruning and shaping tree structure with just a few rules.
Whiting and his research colleagues have been working to develop highly efficient, competitive orchard systems for cherries in response to the escalating costs and tenuous availability of labor. With funding from the Washington Tree Fruit Research Commission, various research projects are focused on different aspects of efficient orchard systems, including rootstock and variety evaluation, development of mechanical harvesting, and development of novel orchard systems.
Big, tall cherry trees turn into complex structures that require significant interpretation during pruning time, Whiting said during the Cherry Institute meeting in January in Yakima, Washington. "These big trees are what keep me awake at night," Whiting said in reference to a very large cherry tree. "When you look at trees like this, it’s hard to decide what’s happening to the management unit and know where to make your renewal pruning that we know we need to make.
"But what tends to happen is that we push the fruiting structure to the top of the tree and then we need 10-, 12-, 14-foot ladders to access most of the fruit," he said.
"It becomes expensive, and there is some question as to whether this type of system is competitive."
In the new orchard system that Whiting is developing, upright fruiting wood and small, repeated fruiting units allow training and pruning to be governed by simple, easy-to-follow rules.
"We need to create a compact wall of fruit that bears fruit on year-one wood," he said. "This concept has an emphasis on dwarfing rootstock and looks a lot like the vertical shoot position training used for grapes."
Whiting said that in a research trial, he had planted whips, training the leader horizontally to a wire. The whips were headed when they were planted.
"But one of the problems with this approach is that you’re still heading the tree," he said. "Every time you head, you’re sacrificing precocity."
To eliminate the need to make head cuts, he is now working with nurseries to make heading cuts at the nursery at around 14 inches and create a tree with a few branches rather than a whip. "We don’t want something feathered, just a tree with a couple of branches." With the new style tree, a grower would have two uprights to begin training on the wire and start filling space between the trees at planting.
He calls the new system "UFO," or upright fruiting offshoots. Thus far, he prefers the trees to be planted at an angle of 30 to 45 degrees because it eliminates some of the problems associated with planting trees upright and bending them. He stressed that the whip should not be headed.
At the end of the first year, you would have upright growths about 12 to 14 inches apart, Whiting explained. "We don’t head the uprights, but instead want to take advantage of the upright growth habits." He noted that vigorous uprights could be headed at the end of year one or tied to be horizontal. Wires should be placed as low as possible because all fruiting wood goes upward from there.
With the whip horizontal, nodes are removed for even spacing of the buds on the upper side of the limb.
"When we go to the second and third year, there will be issues where the node failed to grow," he said, adding that the grower needs to fill the space from the missing nodes. They are working to develop the best techniques to encourage the two-year-old spur to become vegetative.
At the end of year two, the focus is still on the growth of well-positioned uprights, he commented. Renewal cuts are made at the base of the permanent horizontal leader. But heading cuts are still taboo. "Heading creates a complexity that we want to avoid," he said. "Heading begets heading."
He stressed that the system is based on precocious, size-controlling rootstock. Trees are six feet or eight feet apart, with ten feet between rows.
By year three, which would be the first fruiting year, the UFO will have developed into a system that allows for systematic renewal of fruiting wood and precision management of the canopy. It takes advantage of the natural cherry growth habit and has potential to incorporate technology. In the coming year, WSU researchers plan to test mechanical thinning in the new orchard system.
"Every inch of growth from year one that we got in our research and cooperator trials will turn into fruiting wood in year three," he said.
Whiting and his team are assessing the yield and quality of cherries grown under the new system. Fourth- and fifth-leaf evaluations show that the new orchard system can generate high-quality, large fruit. Though a range of cultivar-rootstock combinations are under evaluation, Skeena on Gisela 12 produced "phenomenal" fruit in terms of size and quality in both 2006 and 2007, he said. The fifth-leaf Skeena produced 10.6 tons per acre, with almost all of the fruit at 9.5 row or larger.
In addition to creating a novel orchard system, Whiting has changed the way horticultural research is typically done. Instead of conducting the field trials in WSU research orchards, the project is being done in partnership with growers, with demonstration blocks situated in different parts of the state.
He is looking for more grower-cooperators who are willing to plant two trees or several acres in their orchard as a demonstration.