Pruning Workshop Focuses on High-Density Fruit Planting
BIGLERVILLE, Pa. — With more fruit growers transitioning from large trees to dwarf and semi-dwarf varieties planted in denser systems, the “art of pruning,” as Jim Schupp, director of the Penn State Fruit Research and Extension Center, likes to put it, has changed.
“Six to eight cuts could really make a difference now,” Schupp told a group of around 100 growers gathered at the center Tuesday for a pruning workshop.
Trees in either a vertical axis or tall spindle system are handled much differently than the more traditional large apple trees grown in Adams County.
In both of the denser systems, trees are grown in narrow rows with only a few feet of space between them. Visually, it creates what looks like a fruit wall in the fall and is great for fresh fruit varieties. But the purpose is more than aesthetics. High-density plantings, while more expensive to put in, can result in more fruit production and are designed for machinery and automation technologies for spraying, thinning and harvest.
Pruning still needs to be done by hand, though. And according to Schupp, these new systems can save growers lots of time in work and training since the main focus of both systems in ensuring that a central leader grows healthy, instead of multiple large branches.
“When we talk about the vertical axis, it’s all about the central leader,” he said.
Schupp demonstrated pruning techniques on a vertical axis planting of Honeycrisp apple trees, which were set out in rows separated by 14 feet whith the trees in each row separated by a little more than four feet.
The central trunk of each tree is the focus, with the goal of filling the space between trees, allowing for a good light environment. Between 30 and 36 “secondary branches” should be left on a tree after pruning, he said, and none with a diameter half as large as the diameter of the central leader.
“You need to focus your eyes on really the biggest branches of the tree,” he said.
Trees in a tall spindle system are planted even tighter, usually three feet between trees in rows separated by 12 feet.
In a tall-spindle system, growers have no choice but to cut branches that are more than 1 inch in diameter, simply because there is no room to grow many branches in the first place, Schupp said.
“With a spindle, you must remove big limbs. If you don’t remove big limbs, you will have a big mess,” he said.
Between 30 and 35 secondary branches should be left in a tall spindle.
In both cases, pruning can be as simple as a few cuts, Schupp said, and when you’re talking about training new employees, including Hispanic migrants, it can make a difference.
The systems can also produce more apples on less acreage in less time.
The vertical system at the Extension center has 690 to 700 trees to the acre, while the tall spindle system has around 1,200 trees to the acre.
Each system was planted around 2008, and this past season, the tall spindle produced more than 1,000 bushels of Fuji apples to the acre. Schupp said he wouldn’t be surprised if the system produces 1,500 bushels in 2013, depending on conditions.
But the trees almost have to produce a quick return since they cost so much to put in.
Tara Baugher, Adams County tree fruit educator, said it costs between $10,000 and $12,000 per acre to put a high-density planting in. She said most growers are gradually switching over to high-density plantings because of the costs involved and the time it takes to produce apples.
Timing a pruning, Schupp said, is also important because of changes in temperature. While trees become more hardy as temperatures get colder, sudden warm-ups followed by a sudden cool-down can “shock” a tree, especially if pruning was done recently.
Schupp said growers should pay close attention to the weather and suspend pruning if they think sudden drops in temperature are coming.
The root stock of the tree and the variety of apple are also something to consider. Certain varieties will perform differently in dense plantings, some better, some worse.
The bottom line in high-density plantings, a grower no longer needs a large tree and good pruning skills to do good pruning to get good fruit.
“You don’t need big trees to grow a lot of fruit when you have a lot of trees to begin with,” he said. “In very few cuts, we can do an awful lot of good.”