When trees and shrubs are pruned properly, they are able to add even more beauty to their landscapes, while improper pruning can ruin or greatly reduce their landscape potential. Generally, it is better not to prune than to prune incorrectly. The natural world allows plants to live without pruning for years, but man can ruin what nature has created.
Basics of pruning
Poor pruning methods often cause healthy plants to become weak or deformed. Even in nature, all plants eventually undergo pruning. It may be a simple matter of low branches getting shaded by higher ones, resulting in a collar around the base of the branch that restricts moisture and nutrients from circulating. After the leaves wilt, the branch will eventually drop off due to high winds or storms. During their quest for food, wild animals often break off tender young branches of small plants. Plants organically assume the shape necessary to make the most of light in a particular location and climate over the long run. If one walks into a wilderness and sees the beauty of naturally growing plants, one will appreciate a plant's ability to adapt to a location.
As with any skill, pruning requires knowledge of what you are doing to be successful. A chainsaw or pruning saw does not automatically make one a landscape pruner. Every year, more trees are killed or damaged due to improper pruning than by pests. Essentially, pruning involves removing or reducing certain parts of the plant that are no longer required, that are no longer effective, or that are no longer useful. This is done to supply additional energy to the plant's flowers, fruits, and limbs. There are several definitions of pruning, but essentially it involves removing plant parts to improve the plant's health, landscape effect, or value. If the objectives have been defined and a few basic principles understood, pruning largely boils down to common sense.
Pruning is generally done any time of the year, although the recommended time for certain plants varies. In spite of popular belief, pruning at the wrong time of year does not kill plants, but continual improper pruning causes plants to be damaged or weakened. Prune your plants at the time when they will suffer the least damage, not at the convenience of the pruner. Following this rule makes the plant less susceptible to damage. As a general rule, pruning most plants is best performed in the late winter or early spring before growth begins. It is not recommended to prune immediately after new growth appears in the spring. Developing new growth consumes much of the food stored in roots and stems. In order to prevent a considerable decrease in the plant's size, this food should be replaced by new foliage before it is removed. This is a common problem encountered in pruning for the untrained arborist.
Additionally, late in summer it is recommended to limit the amount of pruning done on some plants since new growth may be encouraged. Cold weather may not have enough time to harden off this growth, resulting in cold damage or winter kill. As soon as possible, prune storm-damaged or vandalized plants or those with dead limbs to prevent additional infestations and diseases.
Cuts should be clean and smooth for rapid wound healing. To achieve this, you need sharp pruning equipment. Avoid leaving stubs as they can cause dieback. When removing large branches, be careful not to tear the bark.
specific pruning techniques
The following provides some specifics on pruning techniques:
Woody plants generally fall into two categories based on the arrangement of their buds on twigs and branches. Generally, the bud arrangement determines the plant's typical growth pattern. Buds may have an alternate or an opposite arrangement on the twigs. An alternate-bud plant usually has rounded, pyramidal, inverted pyramidal, or columnar shapes. A plant with opposite buds is almost always a rounded tree or shrub with a rounded crown. New shoots will always grow in the direction indicated by the position of the last pair of buds. On top of the branch, buds will likely grow upward at an angle and to the side the branch is pointing. As a general rule, it is best to cut each stem back to a bud or branch. Selected buds that point to the outside of the plant are more desirable than buds pointing to the inside. Cutting to an outside bud prevents the shoots from growing through the interior of the plant or crisscrossing.
Select a branch that forms a 45-degree angle with the branch to be removed while cutting back to an intersecting (lateral) branch. In addition, the branch that you cut back to should have a diameter that is at least half that of the branch being removed. Make slanting cuts when removing limbs that grow upward; this prevents water from collecting in the cut and expedites healing.
If you want to "open" a woody plant, cut out some of the center growth and prune the terminals back to the buds that point outward. In shortening a branch or twig, cut it back to a side branch and make the cut 1/2 inch above the bud. Cuts too close to the bud usually cause it to die. When the cut is made too far from the bud, the wood above it usually dies, resulting in dead tips on the ends of the branches. When the pruning cut is made, the bud or buds nearest to the cut usually produce the new growing point. When a terminal is removed, the nearby side buds grow much more than they would normally, and the bud that is closest to the pruning cut becomes the new terminal. Remove the tips of all limbs if you want more branching on the side. Because the roots are not reduced, the strength and vigor of the new shoot are inversely proportional to the amount of stem that is pruned back. The new growth of a deciduous shrub will be vigorous and have few flowers the first year if it is pruned to one foot from the ground. However, if only the tips of the old growth are removed, most of the previous branches are still there and new growth is shorter and less vigorous. The flowers will be more abundant, though smaller. For more small flowers and fruits, light pruning is recommended. Pruning extensively is recommended if fewer but high-quality blooms or fruits are desired in following years.
According to Dr. Alex Shigo, USDA Forest Service plant pathologist, thick and heavy branches should be removed flush with the collar, not flush with the trunk. Chemically protective tissue is found in the collar. In the natural decay of a dead branch, when the decay advancing downward meets the internal protected zone, an area of very strong wood meets an area of very weak wood. The branch falls away at this point, leaving a small area of decayed wood inside the collar. The decay is walled off in the collar. This is the natural shedding process when all goes according to nature's plan. When the collar is removed, the protective zone is removed, resulting in a serious trunk wound. The trunk can then be easily infected with wood-decay fungi. Even if the pruned branch is alive, removing the collar at its base can cause injury.
When cutting branches larger than 1 1/2 inches in diameter, use a three-part cut. The first step is to saw an undercut from the bottom of the branch about 6 to 12 inches out of the trunk and about one third of the way through the branch. Make a second cut from the top, about 3 inches further from the undercut, until the branch falls away. It will then be possible to cut back the stub to the collar of the branch. Branches should be properly roped, supported, and lowered to the ground if they may damage other objects on the ground.
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