Growing Magazine - June, 2009

NORTH FEATURES

Structurally Sound Fruit Trees

Plan ahead to withstand ice storms
By Kathleen Hatt
Photos by Kathleen Hatt.
The severe ice storm of December 11-12, 2008, downed many shade tree branches on the approach to Carter Hill Orchard in Concord, N.H. Well-pruned, structurally sound peach and apple trees in the adjoining orchard lost nary a branch.

“In the great ice storm of 1998, not a single fruit tree in a commercial orchard in New Hampshire was lost,” says Bill Lord, professor emeritus and tree fruit specialist with the University of New Hampshire Cooperative Extension. As far as he knows, no fruit trees in New Hampshire were lost in the December 11-12, 2008, storm either. Ninety-five percent of New Hampshire’s fruit trees are apple, planted in some 60 commercial orchards totaling 1,600 acres. “If a tree is pruned correctly and the tree can support a crop of fruit, it can support ice from a winter storm,” he says.

Although there are many methods and degrees of pruning fruit trees, all have a similar aim: to enable trees to produce exceptional fruit and to promote structurally sound trees. Because pruning reduces the potential for fruit production, minimal pruning is preferable. Therefore, Lord does not encourage super-intensive systems of tree training such as V or Y trellises. Since most regional orchards are diverse operations of tree fruits, berries, pumpkins and other vegetables with a focus on retail sales, few growers have the option of using these intensive systems.

Beginning at the beginning

Select one-year-old nursery trees that are heavily branched (feathered). Dwarf trees are essential because they bear fruit at an earlier age and require much less pruning. Lord suggests planting 360 to 600 trees per acre, depending on the dwarfing rootstocks used and on-site and soil conditions. Except to eliminate branches over one-half to one-third the diameter of the trunk or leader, dwarf trees will rarely need pruning at planting. An especially sturdy apple variety is Gala, a top grower having, by definition, its most vigorous growth at the top of the tree. Of the most common varieties grown in the Northeast, Paula Red is perhaps the most brittle. Although more brittle than McIntosh or Cortland, with proper pruning it too can survive winter ice. Pruning tools should be kept very sharp.

Courtesy of University of New Hampshire Cooperative Extension.
An apple tree should be shaped like a Christmas tree. The tree should have a single trunk (called a leader), a narrow top and wider bottom. This shape allows maximum sunlight penetration into the tree canopy.
Oversized peach tree branches, those over half the diameter of the trunk where they join the trunk, should be removed.

Imagine a Christmas tree

Like a Christmas tree, apple trees should have a single trunk (called a leader), a skinny top, and a wide bottom. Other variations on this basic shape include Central Leader, Spindle Bush Trees or Axis System. By any name, this shape enables maximum sunlight to reach and penetrate the tree canopy and also facilitates pest control. “Pruning is really a four-dimensional art,” says Lord, “the fourth dimension being time. We need to be able to visualize the impact of pruning cuts over time, considering how we want the tree to look and function as it grows.”

Cut it all out

Whenever a branch needs to be pruned, the entire branch should be cut. Cutting off part of the end of a branch is not a solution to whatever structural problem the branch is causing because the branch will grow again. When the branch regrows, it will regrow vigorously and in an upright direction with a crow’s foot at the end of the branch. The unwanted result will be both of shading other branches and delayed fruiting. Hence, heading or tipping cuts (also made by browsing deer) should not be made unless the object is to induce lateral branching.

Yearly dormant pruning should begin as early as the first day of the new year, starting with the orchard’s least desirable trees. Generally, these would be big old standard trees and difficult trees. Trees pruned earlier could be winter-damaged, a result of fluctuating temperatures. Leave the younger and more desirable trees to last to reduce risk of damage, bearing in mind that apple trees first fruit on three-year-old wood and that sunlight is necessary to produce the red apples consumers desire. These trees require the most creative shaping work, a process Lord describes as most satisfying. “An old grower friend once observed,” says Lord, “that pruning should be done by the person who packs the apples because that person would prune to ensure the light penetration that produces red apples.”

Promoting sound tree structure

In the year they are planted, stake trees to promote strong development. Not only will stakes help support trees, particularly dwarf trees that bear fruit young in life, but they will provide an anchor point for lateral limbs in need of spreading. (Clothespins, elastics or specially designed spreaders are also effective tools for opening out new branches.) Nearly flat branches—those at an angle of 60 to 75 degrees—will develop wide, strong crotches and will also be most productive. Stakes should be 8 to 10 feet tall, set 3 feet into the soil. Pressure-treated wood 2 inches in diameter or electrical conduit pipe .75 to 1 inch in diameter make ideal stakes. Soft twine or string tied to a stake may be used to pull lateral limbs in need of spreading. To reduce tree support costs, most growers use a simple trellis or wire support system. A single wire at 6.5 feet ties the support stakes together.

In late winter or early spring of the year after they are planted, some trees may need thinning, particularly when there are laterals that could potentially shade other branches and inhibit flower bud and fruit production. First, remove dead, diseased or damaged wood, then consider removing oversized branches, those which are over half the diameter of the trunk where they join  the trunk. Be sure to remove the branch completely. Also remove branches lower than 20 to 22 inches above the ground, which are likely to produce inferior-quality fruit and interfere with orchard mowing.

In the third year after planting, and in subsequent years, maintain the practices begun in the first two years. Continue training the leader to the stake and cut out any oversized branches. Pruning cuts may increase in size, but practices remain the same. For some upright-growing branches, especially those varieties that tend to grow upright such as Delicious and Macoun, additional limb spreading may be necessary.

A bit about peaches

While only about 5 percent of the New Hampshire tree fruit crop, peaches are becoming increasingly more popular in apple orchards in the Concord area and south. Unsuitable to cold valleys, peaches are restricted to sites elevated relative to the surrounding land so that cold air can flow away.

The first pruning of peach trees should occur at planting, and subsequent pruning is typically done to produce what is called an open center tree. The leader is removed, and cuts in subsequent years made to keep the center of the tree open to light penetration. Pruning should usually be delayed until April so that the survival rate of flower buds (which occur on one-year-old wood) can be assessed.

Other winter tasks

Defoliation about two weeks earlier than usual this fall and well before the December ice storm made it possible to clean and mow orchards early. To promote a healthy 2009 crop, growers should pay attention to deer fences and to monitoring other wildlife invasion, and perhaps hope for a coyote or two to control the vole population.

Some Advice from an Earlier Time

Winter Duties, from New Hampshire Agriculture, First Annual Report of the Board of Agriculture, May 1, 1871, by James O. Adams, Secretary of the New Hampshire Board of Agriculture

Now, without theorizing farther, let me urge the farmer to think when he lays out his fields, when he takes a boulder from the earth . . . to think when sapping weeds and noxious insects make their appearance . . . when he plants or prunes his orchard . . . in short to think of the way and the end, in all the operations of the farm, and all the requirements of his occupation; to study nature and her laws, to investigate . . . the art of agriculture, and to work with the mind while the hands are engaged in labor; to exercise the brain that the muscle may be spared. Then will the farmer find his duties less irksome and his pleasures greatly augmented . . . . Let me entreat you to think—to study more and toil less.

Kathleen Hatt is a freelance writer and a frequent contributor to Moose River Media publications. She resides in Henniker, N.H.