From Ohio State University Extension Fact Sheet, Horticulture and Crop Sciences
by Richard C. Funt
Trellis Espalier System for Supported Apple Trees
With
the advent of size-controlling rootstocks for fruit trees and high
density plantings, growers have developed a renewed interest in trellis
supports for fruit trees. This is especially true with apple cultivars
on the most dwarfing rootstock, M9. Trees trained and secured to wire
trellises have been estab lished in home plantings. This method of
growing apples can accommodate from four to six dwarf trees between two
posts, depending upon planting distances. Most other rootstocks result
in growth that is too vigorous for economical trellis training or are
not adaptable to Ohio soils.
The trellis may be constructed for
three to six or more wires, depending on vertical spacings of the wires
and the ultimate height desired. In most instances, the wires are
spaced 18 to 24 inches apart vertically with the bottom wire 18 to 24
inches from the ground. The height of the top wire is determined
somewhat by the harvesting method to be used. If all picking is to be
done from the ground, the top wire would be six feet from the ground.
If a picking platform or short ladders are anticipated, it could be 8
to 10 feet from the ground.
The cost of available posts of the
desired length would be a determining factor. Posts to carry the wires
may be set before or after planting the trees with the line posts
spaced 35 to 45 feet in the row and located halfway between trees. End
posts should be anchored. The wires, usually No. 9 galvanized or three
to four mm monofilament (not recommended for spur type Delicious),
should be in place and secured firmly to the posts by the middle of the
first growing season.
First Season
Training
begins at planting. If no branches are present near the bottom wire,
head the tree at the height of the bottom wire or four inches below, in
the case of Delicious. This will induce branching just below the wire.
The uppermost new shoot usually grows in an upright position and
assumes the position of a central leader. At least two other shoots
will arise below this one. The two most suitable branches are tied
loosely (plastic ties) to the bottom wire as soon as they are long
enough, one in each direction. Any other shoots are cut back to short
stubs. In tying a shoot to a wire, do not bend it downward to a level
that the tip is at a lower level than the point of attachment on the
trunk. To do so greatly retards extension shoot growth. The shoot will
be in the best position when the tip is a few inches higher than its
base. Also, this position is less likely to induce vigorous risers on
the scaffold (Figure 1). Growth of the uppermost shoot should extend
well beyond the second wire by the end of the first growing season.
Second Season
During
dormant pruning the next spring, head back this central stem at a point
just below the second wire. Branching will occur just below the cut.
Tie two of the lateral shoots, as they develop, to the second wire -
one in each direction. Train the uppermost shoot to the central leader
position. For production efficiency, it is important to cover the
trellis with fruiting wood as quickly as possible. If possible, it is
best to bend by tying shoots that compete with primary laterals rather
than delay fruiting by pruning. The branches trained to the lower wire
need little pruning the second year, other than to maintain terminal
growth and to prevent vigorous upright shoot growth. Strong upright
growth is headed back severely so as to contain it well below the
second wire.
Third and Later Seasons
Pruning
during the succeeding years of training will be similar to that
described for the second year until the basic framework is complete.
When
the central leader reaches the top wire, one of two procedures may be
followed. The leader may be bent in one direction and tied to the top
wire. Then, when a lateral shoot develops below the bend and becomes
large enough, it may be secured to the wire in the opposite direction.
The other procedure is to head the leader just below the top wire. When
new lateral shoots develop, tie the two uppermost to the top wire, as
soon as they have sufficient length, extending each in opposite
directions. The latter method gives a little more assurance of adequate
branches for developing into scaffold branches.
As the arms or
scaffold branches touch those of the adjoining tree, an overlap (10 to
20 percent) may be desirable to insure all portions of the trellis are
covered with fruiting wood. Each year, after the fruiting wood covers
the trellis, pruning should be limited to thinning out to insure good
sun light penetration. Extra scaffold shoots left in during the early
years should be removed gradually over a three to four year period to
permit no more than one primary scaffold per side per wire. Prune side
branches lightly with thinning cuts to maintain the desired three to
four feet width of tree row.
Mature plantings in the
trellised hedge-row system require only a moderate amount of annual
dormant pruning. It is often helpful to go over the planting in August
each year and remove excessive or unwanted shoot growth.
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