Minimal pruning has maximum benefits
Earlier production, fewer picks during harvest, and reduced labor costs are some of the advantages.
Kevin Day describes the minimal pruning technique to IFTA members.
By doing minimal pruning in the first two years, one California grower-shipper is able to bring its stone fruit trees into full production by the third year, three years earlier than traditionally pruned orchards.
At George Brothers, Inc., Dinuba, California, they are looking at all angles to find ways of becoming more efficient in the orchard and reduce inputs and labor costs. They are keeping their peach, plum, and nectarine trees shorter by mechanically topping—to around nine feet tall—to make ladder work easier, and are reducing pruning costs while improving yields.
Irrigation in the Dinuba area is mostly done by furrow because water from the Alta Irrigation District is relatively clean and inexpensive, costing about $30 per acre-feet. For most growers, installing microirrigation systems at a cost of about $1,200 per acre hasn't been cost effective.
Lee Garispe, orchard manager at George Bros., showed how they are using minimal pruning in a block of Zee Fire, an early May nectarine variety, during a field tour of International Fruit Tree Association members. Because of the minimal pruning, they were able to pick fruit three days earlier than other growers with the same variety. Also, they have less summer pruning than with traditional training systems, and can summer prune without ladders. Workers merely snap out the brittle water sprouts as they move through the orchard on foot.
"Our neighbors are picking their trees five times, while we picked ours in three," Garispe said, adding that the trees are wider and shorter and get better light interception than the tall stone fruit tree shapes traditionally grown in California.
Mike George, grandson of one of the three founding George brothers, said they have reduced their labor costs by 25 percent due to the reduced and delayed pruning and shorter trees. George Bros., founded in the 1930s and now run by sons of two of the three brothers, is a medium-sized fruit operation with a packing house and about 1,500 to 2,000 acres of tree fruits and table grapes.
Kevin Day, University of California Cooperative Extension agent for Tulare County, has been working with George and Garispe in developing the minimal pruning system.
In a second-leaf Honey Royale peach block, the inside of the tree looks much like a bird's nest cluttered with small, unpruned branches. But a closer look shows that the inside branches have been twisted and broken, Day explained. By mid-April, shoots are tipped or cut by one-third, and by the middle of June, the tree centers are broken, but left to help push the main scaffolds outward.
"We're trying to put vigor on the outside of the tree by having a congested center for the first two years," Day said. "The only place where we have a light-rich environment is on the outside. If we pruned out the center, the outside scaffolds will grow toward the light-rich center."
Day believes that no pruning is better than bad pruning. "Let's just not prune it at all—it's easier to do without and not do anything. If the system is that complicated and can't be taught to unskilled workers, then it's going to fail."
Because George Bros. are after a big crop in the third leaf, they don't want to do anything in the second leaf that will impact the next year's yield. "Why make a sophisticated horticultural decision if it's not hurting you," argued Day, adding that they don't need to prune to stimulate vigor. "You just end up making the wrong decision. The longer you wait, the easier decision making will be."
Garispe noted that in the third leaf of Honey Royale, they made big cuts in the winter to spread out the tree and clean out the middles. But because they haven't made any heading cuts during the life of the tree, the nodes are closer, and there aren't as many water sprouts.
Day added that studies have shown that it takes two years for a tree with big cuts to catch up with a nonpruned tree.
Sunburn has not been a problem in the minimally pruned blocks.
High density plantings are not common in California's peach, plum, and nectarine orchards, according to Day, who said that 225 trees per acre is considered high density by California standards.
In California, most stone fruit varieties become obsolete within seven to ten years, so growers are not as concerned with appearance, he said. Perfectly shaped trees are not as important in California as in other locations, because growers are not keeping the orchard for 20 years or more.