Horizontal Espalier The horizontal espalier training system consists of a set of horizontal wire trellises attached to walls, fences, or posts. When starting from a whip (seedling with a single slender stem), it is cut just below the first wire. This practice causes new shoots to develop from lateral buds. Two lateral shoots of equal vigor are selected and trained on stakes tied diagonally to the wires (Figure 19–21). These stakes are later (in summer) lowered to the horizontal wires and tied. Stakes may not be necessary. Horizontal limbs are developed by first heading the plant just below each wire. Growth toward the wall should be pruned. Horizontal espaliers produce uneven vigor in the plant. The whole process is repeated to form the next tier of lateral branches. The ends of the lower scaffold branches usually lose vigor. Once established, side shoots will be produced, first on the lower limbs. These shoots are pruned in summer to form fruiting spurs in the next season. As fruiting spurs increase in number over the years, they should be thinned out to avoid overcrowding and reduced plant vigor. Palmette The palmette training system consists of several designs—baldessari, v-form, verrier, oblique, and candelabra. This system is a variation of the espalier system whereby plants are trained at about a 40-degree angle instead of having horizontal branches. The candelabra palmette training system uses a lattice framework consisting of horizontal and vertical arms to create balanced and attractive trees (Figure 19–22). Cordon The cordon training system requires the use of wire, similar to a horizontal espalier system. A single main stem is tied at an oblique angle to the wires. Cordons perform best if the angle is oblique. Laterals, which grow from the main system, are pruned to form fruit-bearing spurs (Figure 19–23). Double cordons (U) and four-armed Kniffen are also used in training plants (Figure 19–24). 19.14.3 PRUNING EVERGREEN BROADLEAF FRUIT TREES Broadleaf evergreen fruit trees are pruned only lightly, especially once established. Species such as citrus and avocado are rarely pruned. Light pruning may be done to control plant height, remove deadwood, and induce fresh growth, as in species such as lemon, coffee, olive, and mango. Citrus and lemon fruits are heavy, and hence fruiting should be encouraged on strong branches to prevent breakage. The productivity of citrus trees declines with age, requiring that trees be rejuvenated by topping and hedging to remove old and weak limbs. FIGURE 19–21 Training and pruning of a horizontal espalier. FIGURE 19–22 Training and pruning of a candelabra palmette. 19.14 Training and Pruning Fruit Trees 599
FIGURE 19–23 cordon. Training and pruning of a FIGURE 19–24 system. A four-armed Kniffen training 19.15 COMMON TREE PROBLEMS As trees and shrubs grow and age, they develop characteristics that reduce their visual appeal or pose problems in the general environment. Many of these problems can be corrected by pruning. The major ones include the following: 1. Excessive height. Ornamental trees in open space are normally allowed to grow freely to attain maximum height. Excessive tree height becomes a problem if it interferes with utility lines or overwhelms structures such as buildings. When this happens, the height of the tree may be reduced by drop crotching (cutting a main branch on the leader back to a lower crotch). 2. Excessive spread. When large branches located high on the tree spread excessively, they become prone to damage by wind. The condition may also cause the tree to be deformed and lose its visual appeal. When branches spread excessively, limbs from the highest and outermost parts should be pruned. 3. Low-hanging limbs. Low-hanging limbs pose clearance problems for humans and vehicles. It is desirable to establish clearance early in the growth of the plant. 4. Deadwood. When deadwood occurs, it should be removed to prevent disease infestation and spread. Deadwood also detracts from the beauty of a tree. 5. Overcrowding of trees. As trees grow and mature, they take up more space in the landscape. That is why it is critical to know the mature characteristics of trees before installing them in the landscape. Overcrowding can reduce the aesthetic value of plants considerably. It also causes trees to compete for light and thereby grow excessively tall. Their natural shapes and forms are often ruined. The remedy to overcrowding is complete removal of trees or pruning of limbs. 6. Forked trunk. A forked trunk stands the danger of splitting in strong winds to produce unsightly results. Unless there is an overwhelming advantage to maintaining two leaders, landscape trees should be trained early to have one trunk and wellspaced scaffold branches. Only a few (four to six) scaffold branches should be maintained. All other branches arising directly from the trunk should be removed. 600 Chapter 19 Pruning 19.16 TRAINING AND PRUNING SMALL FRUIT TREES Small fruit trees may be trained and pruned to be standard sizes, thereby bearing fruits at a higher level for easy picking. Small fruit trees require some pruning to bear quality, large fruits and have high yield. Two groups of small fruit trees may be identified in terms of pruning and training needs—cane and bush fruits.