Achieve the right ratio of wood and buds in cherry trees
As with apples, researchers have found that dwarfing rootstocks for sweet cherries and higher-density planting systems can lead to increased profit margins for growers, said Greg Lang, a horticulturist with Michigan State University (MSU).
Cherries are Lang’s specialty. He recently demonstrated proper pruning of high-density cherry trees at Coloma, Sparta and Traverse City, Mich., with Lynn Long, a horticulturist from Oregon State University. Long is a sweet cherry specialist who conducts work in The Dalles, Ore., the most concentrated sweet cherry-growing area in North America, Lang said.
The highest-density system is super spindle axe (SSA), which calls for spacing of 2.5 feet between trees and 11.5 feet between rows. That gives growers a density of roughly 1,500 trees per acre. With this system, Lang said Gisela 3 and Gisela 5 rootstocks work best.
“The goal is to make that ‘fruiting wall’ everyone is going for,” Lang said. “The SSA system, if managed right, can give you five times as much production as a tree grown on seedling roots, and get into production much faster.”
SSA
Lang and Long both like the SSA system. So does Rodney Klenk, owner of Klenk Orchards in Sparta, Mich., who liked it enough to plant his new trees that way. Lang used those young trees to demonstrate pruning techniques.
“You have to be aggressive with pruning,” Lang said, “especially when establishing the trees.”
Selecting the limb you want to be the central leader is very important, Long said, noting that it may not be the tallest limb going up.
“What you’re looking for is one with the right ratio of wood and buds,” Long said. “You can then go and pinch off any buds you don’t want as shoots.”
Growers choose this system to get the best fruit possible, Lang said. It works by forcing the tree to grow fruit rather than wood, through pruning back lateral shoots to a basal vegetative bud.
“This will keep back any overly vigorous shoots, but you still want to maintain enough vigor in the tree to obtain 24 to 30 inches of growth from the lateral shoots,” Lang said.
A tree roughly 8 feet tall by the second year, with light, feathered limbs of mostly new growth and good clusters of fruiting buds is optimal, Lang said. Tight, dense clusters of fruiting buds should be avoided because the quality of the fruit goes down.
Upright shoots, pendant fruiting shoots, weak shoots and any shoots with excessive blind wood that is unproductive should also be removed, Lang said.
The demonstration moved to older, low-density plantings that Klenk uses for u-pick.
“What you want to end up with is a mature tree that has productive wood, the right balance of shoots and buds,” Long said. “Even on trees not in high-density systems. Prune them back to a ‘pyramid’ shape and you’ll see more productivity.”
Late-season pruning
The group moved on to higher-density plantings at Joe Rasch’s orchard, also in Sparta, Mich.
“I’m an apple grower,” Rasch said. “I didn’t really know what I was doing with these cherries at first, but I don’t like big wood, so that’s how I’ve been pruning them.”
Lang and Long were especially interested in Rasch’s practice of pruning later in the year to avoid canker, a common problem with cherries. Rasch had heard about it during an International Fruit Tree Association tour in Chile.
“I figured it was worth a try,” Rasch said.
Lang, who said he was quite interested in the use of summer pruning to avoid canker, is doing some research on it now.
MSU has more information at www.cherries.msu.edu. Greg Lang and Lynn Long have more materials, as well as videos of pruning demonstrations, at www.giselacherry.com.