Peach trees with a pillar growth habit can be planted much more densely than standard peach trees to reap some of the benefits of intensive orchard systems. Photo by Geraldine Warner
New peach varieties with upright growth habits give growers the opportunity to plant peach trees at high densities, without needing a dwarfing rootstock.
Why plant high-density peaches? For the same reasons growers have planted high-density apples, says Dr. Ralph Scorza, plant breeder at the U.S. Department of Agriculture’s research lab in Kearneysville, West Virginia.
Advantages include greater efficiency in pruning, spraying, thinning, and harvesting, and the possibility of mechanizing some practices to reduce labor costs. Mechanization will be difficult if growers simply try to fit the machines into the way they’re growing peaches today, he said.
High-density systems also allow better light interception, giving better yields.
“It’s been very dramatic in apple production, where they’ve used dwarfing rootstocks, and I don’t see why we can’t be doing that kind of thing in peaches,” Scorza said during the International Fruit Tree Association’s annual conference.
But previous attempts to grow peaches on high-density systems have produced mixed results.
Plantings of peaches with a standard growth habit can become difficult to manage as the trees get older, he said. “As they get older and older, it gets harder and harder to keep them in their allotted space. We were trying to take a peach tree that grows a certain way and squeeze it into a system it didn’t naturally grow into.”
About 20 years ago, after seeing the results of many pruning and training studies on peaches, Scorza realized a new approach was needed.
In peach germplasm collected from around the world, Scorza found different growth habits, including dwarfing, compact, upright, and weeping. He picked out cultivars with columnar growth habits and crossed columnar trees that had inferior fruit quality with trees that had good fruit quality, to produce new cultivars.
Scorza has several in the pipeline and has already released two new commercial varieties:
—Crimson Rocket, which has a columnar, or pillar growth habit and is a very narrow, upright tree. It is a midseason freestone peach with 2.75-inch fruit that is firm and highly flavored, with 80 percent blush; and
—Sweet-N-Up, which naturally grows in an upright manner. It is not as spreading as a standard tree, but not as narrow as a pillar tree. It is a highly flavored freestone peach with fruit 3 inches and larger.
In trials, now in their eighth leaf, Scorza and research horticulturist Dr. Steve Miller are comparing pillar, upright, and standard peach trees. All three types were planted at four row spacings (5, 6.5, 13, and 20 feet apart) on central leader and multileader systems.
The canopy width of the pillar trees is 7 feet, compared with the 14-foot spread of the standard trees. The pillar trees have narrow branch angles, which makes them a natural fit for close spacings because they don’t tend to grow into each other. Scorza said they could be planted as close as 4 feet apart to form a hedgerow.
But Miller said he prefers the upright trees to the pillar trees because they’ve been more productive, are easier to manage, and produce large fruit.
In the trial, the upright trees have yielded between 700 and 800 bushels per acre from the fifth leaf on, compared with less than 600 from the pillar trees, and about 400 from standard trees, which are Harrow Beauty.
The upright trees tend to yield a year earlier than the standard trees. No support system is used, he said, because that just adds to the expense. “We’ve had no major limb breaks in the uprights or the pillars. In the standards, we’ve had a few limbs break under the crop load.”
Miller said the upright trees were a little easier to prune because the growth habit is closer to a standard tree, and they don’t have such narrow crotch angles as the pillar trees.
If upright trees were planted 5 to 6 feet apart and trained to a perpendicular V or Y system, rather than a central or multiple leader, he thinks yields could reach as high as 1,200 or 1,500 bushels per acre with fruit size of 2-3/4 to 3 inches. Those kinds of yields are possible with processing fruit grown on large trees, but for fresh fruit that would be an extremely high yield, Miller commented.
Though both the upright and pillar trees in the trial are narrow, they are as vigorous or possibly more vigorous than standard trees, Miller said. He recommends that growers not plant them on vigorous sites with deep soils. His advice is to plant them on less vigorous—though not necessarily poor—sites.
In the next test planting at Kearneysville, which will include some new selections, he’ll try using a V system, which he thinks will eliminate some of the shading problems he’s seen with both the upright and pillar trees in the current trial.
He thinks some of the newer pillar and upright selections that will be tested are likely to be less vigorous. Scorza said they cover the gamut of yellow, white, low acid, high acid, and high sugar varieties, and ripen in all seasons.
Though he’s still breeding through hybridization, he’s using molecular markers to select for the upright and pillar traits. The pillar type has two copies of a columnar gene in its genetic makeup. The upright type has one columnar gene, and the standard type has no columnar gene.