4. Pruning may be done to reduce the number of fruiting branches per plant (thinning out) in order to increase fruit size and quality. 5. Generally, proper pruning enables a fruit-bearing tree to produce higher-quality fruits over a longer period. Flowering plants also produce bigger flowers over a longer period of the plant’s life when pruned. 6. Properly pruned trees have good fruit distribution throughout the plant canopy (not only at the edges) and bear fruit of good size, color, texture, and sugar content. 7. Pruning allows the gardener easier access to fruits during harvesting. 19.2.4 PHYSIOLOGICAL OBJECTIVES Pruning, if not done judiciously, may have adverse physiological consequences on plant growth and development. However, pruning may be employed to manipulate plant physiology in a variety of ways to enhance the performance of the plant: 1. Pruning roots before transplanting reduces the chance of transplanting shock. 2. Pruning shoot tips in species with apical dominance (e.g., apple, pear, and cherry) induces lateral branching and thereby prevents the tree from growing straight without sufficient branching. 3. Pruning deciduous species during the dormant period in winter conserves the plant’s stored food for use in spring for vigorous new growth. 4. Severe pruning may have a dwarfing effect on a plant by reducing total vegetative growth. 5. Older plants may be rejuvenated by pruning to stimulate new growth. Apart from these four general purposes of pruning, the procedure may be employed on specific occasions for practical reasons. For example, when plants grow bigger and exhibit destructive tendencies such as roots cracking pavements or foundations of buildings, roots clogging sewage pipes, and branches destroying the roof or touching utility cables, the affected plant parts need to be pruned to contain the plant in the available space. 19.3 PLANT RESPONSE TO PRUNING Removing vegetative parts of plants affects certain plant physiological processes and subsequently growth and development. The two basic plant responses to pruning are described in the following sections. 19.3.1 INTERFERENCE WITH APICAL DOMINANCE As previously stated, apical dominance of terminal buds suppresses the growth of lateral buds. The removal of terminal buds removes this inhibitory effect, allowing lateral buds to grow. In certain plants, gardeners deliberately remove terminal buds (pinching or pinch pruning) to encourage lateral bud growth so that plants look fuller and more appealing. The vertical shoots that arise on the upper side of branches, called water sprouts are an example of a plant response to interference with the process of apical dominance. Pinch Pruning Breaking by hand of the terminal bud. 19.3.2 GROWTH STIMULATION A physiological balance exists between the top and bottom growths of plants. Removing parts of the top growth upsets this balance. Plants respond with a burst of new growth, especially just below the cut. In spite of the new growth, pruned plants do not exceed the size of the plant before pruning. This dwarfing effect on plant size occurs because the amount of new growth does not match what was removed in addition to what would 19.3 Plant Response to Pruning 569
have been produced by the plant in its prepruned form. Similar to the practical application of interference with apical dominance, gardeners employ this dwarfing effect of pruning in creating art forms. The epitome of such an art form is the Japanese art of dwarfing plants called bonsai. 19.4 PRUNING TOOLS Most pruning tools are handheld and operated manually. A motorized chain saw may be used for cutting large branches. Cuts are made by either sawing or scissor action of cutting tools. Pruning tools are hence a variety of saws and shears designed to cut different sizes of limbs at different heights and different locations on the plant. When the plant is tall and the limbs are hard to reach, pruning aids may be used to lift the operator to the desired height. Some of the common pruning tools are described in the following sections. 19.4.1 SHEARS Figure 19–1 shows a variety of shears. Hand Shears (Hand Pruners) Hand shears are the most commonly used pruning implements. They can be held in one handand are available in two basic designs. One design has a true scissor-cutting action produced by two cutting edges or blades (bypass action type). The other design uses one sharp blade that cuts against a metal piece (anvil type). The limitation of this tool is that it can only cut limbs that are less than 1/2 inch (1.3 centimeters) thick. Loppers Long-handled shears operated with two hands and used for cutting larger branches. Lopping Shears (Loppers) Lopping shears (loppers) are designed to cut larger branches (up to 2 inches or 5.2 centimeters in diameter) by a two-handed action. Their long handles provide the needed leverage for cutting thicker limbs. The long handles also extend the reach of the operator so that limbs located high on the stem may be pruned without using a pruning aid such as a ladder or lift. Short-handled loppers are available. The common loppers have hinge action, but more expensive designs with different types of action are available. Hedge Shears Two-handed tools, hedge shears are designed for trimming and shaping hedges and ground covers. Manual models are common, inexpensive, and easy to use. Electric models are also easy to use and have a fast-cutting action. However, they may be frequently jammed by twigs during operation and also be limited in operation by the length of the extension cord. FIGURE 19–1 A variety of shears used in pruning. The type used depends on the size of the branch. 570 Chapter 19 Pruning
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