The optimal orchard starts with the hottest variety out there, said Belding, Michigan, grower Ed Wittenbach. While Honeycrisp is currently the hottest variety, that can change, he said. The trees in an optimal orchard are planted on an ideal site, with a planting system to intercept the maximum light. "For me, it’s single row," he said, adding that he would probably plant about 1,000 trees per acre. "I’d want to put them on wire, with the trees to be central leader on top and wider on the bottom like a Christmas tree."
The orchard would have irrigation and frost protection, but not hail netting.
"I would want to achieve maximum production by the fourth leaf with about 50 bins per acre of high-quality fruit," he said. "I would grow it on M.9 rootstock with tree height 10 to 12 feet. Though ladder work is –minimized, you’d still need a few ladders."
"The optimal orchard would probably be Honeycrisp planted on Budagovsky 9, and trees would be spaced two feet between trees and 13 feet between rows," said Fred Koenigshof, an apple, peach, and raspberry grower from Coloma, Michigan. Koenigshof, the new president of the Michigan State Horticultural Society, has about 60 acres of apples, 50 acres of peaches, and 50 acres of berries that are sold by his wife, Linda, at farmers’ markets in Chicago. Some of their production is marketed through the Waterlake Fruit Exchange, a grower cooperative.
Koenigshof said he would prune his fruit trees based on the diameter-rules pruning –system. He explained that, "Diameter-rules pruning means that you take anything that is larger than half the diameter of whatever it’s coming off.
For example, if wood is coming off the main trunk, it can be more no more than half the diameter of the main trunk. "Some call it slender –spindle. It’s a real simple system. That way you’re renewing wood all the time, and you can get rid of that heavy wood."
Trees would be supported by a three-wire trellis with 12-foot posts. The central leader trees would not be allowed to grow taller than the top of the posts.
Platforms should work well in Koenigshof’s optimal orchard as well as new spray technology that goes over the row with a recapture system. The orchard would have 1,500 to 1,600 trees per acre.
Comstock Park, Michigan
Steve Thome, apple grower from Comstock Park, Michigan, said that the optimal orchard would be a "fast producer," with some apples picked in year two. He would keep his trees no taller than ten feet to minimize ladder use, but the trees would be picker friendly. Diameter-rules pruning would be the pruning system. "Diameter rules will help everybody from thinning to pruning," he said. "It’s an easy tool to explain to workers. When the diameter gets too big, you get it out."
He believes that mechanization will come in the future. "But you have to have a big enough orchard and have enough acreage to afford it. Its use has to be effective and economical."
He would grow his trees in a slender, columnar shape. The constant renewal of wood would provide good light interception, which is important to growing high-quality spurs.
Thome would space his trees three by nine feet apart. Target production is 1,000 bushels per acre or about 50 bins per acre, he noted.
"I would use highly feathered trees, grown on a two- or three-wire system," Thome concluded.
As McDougall & Sons has replanted its orchards over the past 15 years, it has been transitioning away from expensive systems, such as the modified Tatura trellis, to simpler, more pedestrian systems, said company horticulturist Brent Milne. The goal is to be ready to use platforms to move workers and ultimately segue into robotics when they become available, Milne said. Trees are on Malling 9 or Budagovsky 9 rootstocks.
McDougall is currently planting trees two to three feet apart on a five-wire vertical trellis to create a fruiting wall. Rows are spaced ten feet apart to bring the fruit within easy reach of the pickers. While establishment costs for such intensive plantings are higher, they come into –production more quickly and generate greater yields at maturity, Milne noted. "We’re aiming for a minimum of 50 bins per acre. That’s an average minimum year after year. Hopefully, we’re hitting some home runs where we get 70-plus bins per acre."
With such a narrow row spacing, it takes great diligence to ensure that the tree limbs don’t extend more than 15 inches into the drive row, Milne said. However, the system is designed to make pruning simple and less management intensive so that the pruning crew can build their productivity quickly. Large limbs are removed to promote renewal of short shoots.
McDougall expects that tree training systems will continue to evolve in order to take advantage of future technology. For example, someday, advances in genetics may allow trees with specific internode lengths to be developed so that systems can become less random and more mechanized.
Mike Robinson, general manager at Double Diamond Fruit Company, finds that a vertical trellis with trees spaced 5 feet apart and 12 feet between rows works best for most varieties.
He thinks tighter spacings of, say, 8 or 10 feet between rows, would make it difficult to adopt mechanization. To allow room for fruit-handling equipment, the trees could not extend much into the drive row.
"I don’t want to get in a position where I’m trying to contain the tree into a very small space and if anything goes wrong I’m in trouble," he said. "I’ve been down the super-high-density road, and everything’s fine as long as it works, but I’m not that confident."
With a super-high-density system, a miscalculation in chemical thinning or frost damage that results in a crop loss can lead to vigorous tree growth. Then, the grower has to cut the trees to try to fit the tight space.
Robinson said he settled on the 5-foot in-row spacing because he likes branches to be 2.5 feet long and not overlap. "I don’t see a gain in having a lot of branches on top of each other," he said.
In a new planting, he starts with a trellis wire at three feet, then adds more wires at 5 or 6 feet, 8 feet, and 10 feet. The posts are 11 feet out of the ground. The lower wire is eventually removed so that crew supervisors can move laterally through the orchard. "It’s hard to get good supervisors, and after three hours of crawling under wires, the bin checkers can lose their enthusiasm," he said.
Robinson believes that mechanization will drive more changes in orchard design and that there will be optimal configurations to accommodate robotic equipment. These will involve the planting distance, the density of the canopy, and the precise placement of branches.
"At some point, those optimal designs will have a competitive advantage," he predicted.