Issue link: https://read.dmtmag.com/i/283151
W hich is the best way to grow apples—on a vertical or angled canopy? It depends who you ask. During a debate at the Washington State Horticultural Association's annual meeting, growers leaned towards an angled system, while researchers stood up for the vertical approach. Dr. Terence Robinson, horticulturist with Cornell University, New York, said he favors the vertical tall spindle system partly because of its simplicity and partly because he believes it has the potential to be the most profitable system, if everything goes right. It is simple because it uses the natural characteristics of the apple tree. It is easy to manage and can produce high- quality fruit without the expense of a lot of branch manipulation, said Robinson, who has been experiment- ing with the system since 1991. "If you start with a very nice tree, it's almost an instant orchard," he said. "It will start producing fruit without you doing very much. I say it's as easy as getting up in the morning and falling out of bed to grow the tall spindle." Limb removal The system is based on keeping the diameter of the branches small. The tree has fairly substantial scaffold branches in the first two to five years. Then begins the process of eliminating one or two of the large branches every year. Robinson acknowledged that varieties differ in their response to limb removal. Some varieties generate better renewal shoots from those cuts than others, but the response also is related to the vigor of the tree. For example, if it's a low-vigor Honeycrisp tree, it might be difficult to get replacement shoots to pop out, so the tree might need to be kept more vigorous than otherwise. Robinson used to remove limbs with angled cuts fairly close to the trunk, but he now recommends leaving longer stubs to encourage regrowth. Trees are not headed at planting. Nurseries might tip the trees for shipping, but should be encouraged not to. Most of the time, the trees will grow well, but occasionally, the leader will set a terminal flower bud. Robinson said this should be eliminated as soon as possible. He stressed that heading is not a solution for a tree that's slow to grow. "You might think you're getting a lot of growth when you head, but it basically grows back to where it was before. You don't make the tree bigger," he said. Better solutions for promoting tree growth are to intensively manage water and nitrogen applications for the first two years. Dr. Stefano Musacchi, horticulturist with Washington State University, has been focusing for the past several years on biaxis trees grown in a fruiting wall system. Thin canopies maximize light interception, which usually maximizes dry matter, and that's important because 70 percent of the dry matter the tree produces goes to the fruit. If the canopy is more than three feet deep, there can be problems with shading, lack of fruit buds, and poor-coloring fruit in the interior of the canopy. In the biaxis system, each tree is grown with two lead- ers, rather than one trunk, which helps divide the tree's energies and control its vigor, particularly in fertile soils. Other advantages of the two- dimensional system include high productivity, less shading, better fruit color, uniform production throughout the canopy, and the potential for mechanical pruning and thinning. Musacchi said mechanization is a key issue. Platforms are becom- ing the most important equipment in the orchard because they can be used for pruning, hanging pheromone dispensers, harvesting, and other orchard tasks. Mechanical pruning in summer, timed when the shoots have 12 leaves, has a very positive effect on flower bud formation, he reported. It also reduces the need for pruning in winter, a time when it will stimulate strong regrowth. Summer pruning can be done mechanically with only six hours of labor per acre. In the winter, all that's needed is touchup pruning, which is relatively inexpensive. Higher production John Verbrugge, owner of Valley Fruit Orchards based in Wapato, Washington, said he favors angled canopies because of greater light pen- etration in the bottom of the tree and higher production. He also feels he's better able to optimize the amount of size 72 to 80 premium fruit, the sizes and grade the market prefers. "There's a lot of opportunity to hit the sweet spot better than what we've seen on the spindle systems," he said. Although a V system is more expensive to establish, it pays off because keeping the tree trained to the wires creates efficiencies, Verbrugge said. "It's easy to tell people that branches stay on the wire and nothing in 42 APRIL 1, 2014 GOOD FRUIT GROWER www.goodfruit.com Angled or upright? "You have to find a system you like." —Dr. Terence Robinson PHOTO BY TJ MULLINAX Debating apple growing systems are (from left) Bruce Allen, John Verbrugge, Jeff Cleveringa (moderator), Craig Hornblow, Terence Robinson, and Stefano Musacchi. Growers and researchers weigh in. by Geraldine Warner