Pruning and Training to a Trellis
Trellising is a means of supporting dwarf apple and pear trees to increase their bearing surface and hence their production. The trellis consists of a series of wires supported by posts (Figure 4.8). Limbs and branches are positioned on this wire fence to encourage fruit production. Varieties on M.27, Bud.9, M.9, or M.26, as well as pears on Quince C rootstock, can be trained to a trellis.
Constructing the Trellis
The trellis should be in place before the trees are planted. In the home orchard, 8-foot posts are driven 2 feet into the ground and spaced every 15 to 20 feet apart depending on the amount of space available and the number of trees to be planted. Four wires spaced 18 inches apart, or three wires (no. 9 galvanized wire or stronger) spaced 24 inches apart are strung across the posts. The wire can be fastened to the posts by fence staples, or 1/4-inch holes can be drilled through the posts and the wire passed through the holes. The top wire can be either stapled to the top of the post or strung through a hole drilled 1 inch below the top. End posts will need additional anchoring using a deadman such as that used on telephone poles.
To train trees to a trellis, start by planting the trees 6 to 7 feet apart between the supporting posts (see Figure 4.8). Plant the first tree 4 feet from the end post. Remember to keep the graft union above the ground. Head the tree off just below the bottom wire and loosely tie it to the same wire. Allow young shoots to develop and loosely tie them to the trellis wire in the spring and early summer. Some shoots will develop that are not in the plane of the trellis (projecting away from the wire). These shoots should be pruned off or bent and tied to the wire so they fit the plane. The shoots should be tied to the trellis so they form a 45-degree angle from the main trunk. Allow one shoot to grow straight up. This will be used to develop succeeding levels of branches.
After the first growing season, prune back the terminals of the tied limbs as well as the central trunk. Remove undesirable limbs. Pruning after the second growing season should be similar to that done after the first season. Your goal should be to fill up the trellis area with limbs before heavy fruiting begins. Remove all fruit during the first 2 years following planting to encourage tree growth. The onset of fruiting will reduce the amount of pruning necessary.
Periodically, limbs get old and production decreases. If a limb starts declining, prune it out by cutting it back to a stub close to the main trunk, and train a new one to take its place.
Girdling can result where the limbs and trunk are tied to the wires. Periodically check these ties to make sure that they are still loose and not binding.