Growing Magazine - June, 2009
Structurally Sound Fruit Trees
Plan ahead to withstand ice storms
|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
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,