Upright wall trellis system reduces labor while boosting cherry fruit quality
By Renee Stern
Cherry orchards of the future may be rows of single fruiting walls down which workers drive mechanical harvesters and pruning platforms.
Northwest apple growers and California peach growers already have incorporated fruiting walls' higher density and greater uniformity than conventional orchards into their operations. Now, Washington state and Michigan researchers are adapting the concept to cherries.
By training cherries onto a trellis to create angled or vertical fruiting walls, growers narrow their management units from a tree to a single fruiting upright and repeat that uniformity throughout the row, says Matt Whiting, assistant horticulturist at Washington State University's Irrigated Agriculture Research and Extension Center in Prosser.
"I want a system where labor inputs are not as complicated or physically demanding," says Travis Allan, orchard operations manager for Allan Bros. Inc. in Naches, Wash. "I hope to get (pruning) down to one guy on the ground with loppers."
Fruiting walls have the greatest potential to incorporate new technology, with mechanical-assist equipment and machine harvesters topping the list, Whiting says.
Labor, especially at harvest, is cherry growers' single biggest expense. With labor shortages also a major concern, innovations that increase worker productivity garner plenty of interest.
Bob Harris of Harris Farms Inc. in Moxee, Wash., focuses on mechanization, but says engineering the machines is only part of the task. Without a complementary orchard system, harvest aids and mechanical harvesters won't be cost-effective.
It's a race to produce a working model "before it gets to the point where we don't have enough people to pick the crop," Harris says.
Mechanization also is spurring research in Michigan for both fresh-market sweet cherries and tart cherries for processors, says Greg Lang, horticulture professor at Michigan State University in East Lansing.
Last summer, Lang began brainstorming harvester designs with MSU horticulture professor Jim Flore and research specialist Richard Ledebuhr. A prototype tractor-pulled, beside-the-row harvester showed enough promise to divert tests into fruiting walls.
Whiting has teamed with Allan, Harris and other growers in three years' work to train fruiting wood into vertical or angled uprights. Initial trials created walls at 55- to 65-degree angles, with vertical fruiting uprights spaced about 18 inches apart.
This spring, they're trying an alternate configuration that takes advantage of cherry trees' apical dominance by running two permanent scaffolds with fruiting uprights on wire.
"We're definitely learning as we go," Whiting says. "There won't be one system to fit all situations." Instead, growers will adjust the system to fit the vigor and precocity of their rootstock and scion combinations.
Cherries tend to grow upright branches rather than laterals, a plus with this architecture, Whiting says.
To produce fruiting walls, "We (now) want something in a scion that doesn't have a lot of lateral branching, which is directly opposite of what we've been looking for in the past," he says. "We're rethinking varieties we've discarded over time because they weren't grower-friendly."
Lapins, for example, have desirable upright growth habits, he says. Bings, too, perform well in fruiting walls. Third-year yields for Bings on Gisela 12 rootstock averaged 3 1/2 tons per acre, with 98 percent of the crop reaching sizes of at least 10 1/2 row.
The more open canopy improves light penetration, which should boost fruit sugar, Lang says. Reduced shade on fruit also may enhance firmness to some processing varieties such as Montmorency, which can suffer significant damage when shaken from trees during harvest.
Lang and Whiting say the changes to tree canopy also should provide better spray coverage.
"The older systems require more material and water to blast through multiple layers of canopy," Whiting says. With fruiting walls, growers don't have that vegetative density.
That provides potential for targeted sprayers and visioning systems for more advanced harvest and pest or disease control technology, he says.
Another technical innovation could be over-row systems that spray downward for better penetration and reduced drift, Whiting says.
The expense of establishing new orchards that incorporate the system may be the biggest drawback, he says. But the precocity and yields alone soon pay for the investment—even without considering labor savings.
And, Harris says, the choice soon will come down to investing the money in new orchards or shutting down altogether because of labor shortages and increasing labor costs.
Economic factors have drawn Morgan Rowe, owner of Rowe Farms in Naches, into joining Whiting's research this year with a newly planted test block of Selah cherries on three different rootstocks.
He hopes to produce more high-quality fruit with less labor, reducing his cost per pound.
"With lower density, you have to crop the tree more," Rowe says. "It's easier to get tonnage with higher-density plantings."
Two- and 3-year-old wood provides the best fruiting potential, Allan says. Fruiting walls eliminate more nonproductive structural limbs and cycle faster to that desirable fruiting wood.
One process requiring long-term study is the way in which trunks intercept and translate the force of shaker-harvesters as trees age and grow woodier nonrenewed structures, Lang says.
That may force growers to replant orchards more frequently—but economic gains from more efficient operations may make a shorter cycle feasible, he says.