What is topping? Topping is the indiscriminate removal of tree branches above a certain height with little consideration for the tree's structure or health. Tree branches are cut back to stubs or smaller branches that are not large enough to sustain the remaining branch.At times, homeowners think topping is necessary because trees have become too large for their property and therefore present a hazard. However, topping is not a viable method for reducing a tree's height and actually increases the hazards presented by the tree.

Why topping hurts trees:

• Topping stresses trees - The process of topping often results in the removal of 50 to 100 percent of the leaf-bearing crown of the tree. Leaves act as the food factories of a tree, and removing them can temporarily starve a tree. Trees respond by producing shoots that grow quickly (up to 20 feet in one year) and are prone to breaking. A tree's survival is dependant on its ability to send out new shoots. If the tree is unable to produce a new crop of leaves quickly it will be seriously weakened or die. Depending on the species a topped tree can linger for years or die quickly. One such species is the Beech Tree; due to its inability to sprout readily after topping, it will die in a short period of time. The stress of topping also makes trees more vulnerable to insect and disease infestations. Large open wounds expose the sapwood and heartwood to attacks.
• Topping causes decay - Trees are naturally able to close wounds and compartmentalize or "wall-off" the spread of decay provided the tree is healthy, the cuts are made at the correct location on the tree, and the cuts are few and small. However, the many large cuts associated with topping prevent trees from adequately resisting the spread of decay. The tree is forced to use an excess amount of stored energy in an attempt to produce enough of the chemical compounds needed to resist decay; wound closure is minimal at best. Few trees can defend against the multiple severe wounds caused by topping; decay spreads and overall weakness and decline ensues. A tree with excessive decay is unhealthy, unsafe and is considered a liability. Wound dressings such as tar or paint have not been proven effective in preventing entrance of disease causing organisms nor stopping the spread of decay.
• Topping can lead to sunburn - Leaves act as a tree's natural barrier from sunlight. When a tree has been topped, the leaf-bearing branches have been removed, leaving a tree exposed to high levels of light and heat. The result of sunburn can be damage of the tissues beneath the bark, which can lead to cankers, bark splitting, and death of some branches. This is especially true of thin-barked species.
• Topping makes trees ugly - Besides the harm it can cause your tree, a topped tree can be an eye-sore. Topping both destroys the natural form of the tree and creates stubs where branches used to flourish. Without leaves, the tree appears disfigured. Once a tree has been topped, it will never fully regain its natural form and beauty.
• Topping is expensive - Topping costs the homeowner in more ways than just the initial expense. A topped tree will require further attention much sooner than expected - it will either need to be reduced again because of the weak and fast growing shoots; dead or damaged parts will need to be cleaned up (especially after storms); or a dead tree will require removal. Topping also has a hidden cost in the form of diminished property value. Healthy, well-kept trees can increase property values by 10 to 20 percent, but topped trees are considered an impending expense.
• Topping trees are a potential liability - Topped trees are prone to breaking and can be hazardous. Since topping is not an acceptable pruning practice, a homeowner may be found negligent in a court of law for any damage caused by the branch failure of a topped tree.

What are the options? Reducing the height or spread of a tree is not ideal due to its purpose of controlling a tree's size and preventing the tree from reaching its potential. There may be times however when crown reduction is necessary - providing clearance for a new utility line is an example. The International Society of Arboriculture (ISA) suggests the following recommended pruning practices:

• Pruning cuts should be made at the branch collar, located at the limb's point of origin. This area will promote a strong boundary against decay. If a branch must be shortened, it should be cut back to a lateral limb that is at least one third the diameter of the limb being removed. This method helps to preserve the tree's natural structure.
• Make cuts cleanly, ensuring they are not too large or numerous. 
• The best way to manage trees is to consult with a Certified Arborist. An Arborist is trained to provide the best care for your trees and can provide the service of a crew knowledgeable of current safety practices.

Make careful choices. Selecting the right tree for your property will prevent a number of problems and help to negate the costs of upkeep. It is important to know how large the selected tree will grow and provide sufficient space for it to mature naturally. It is also important to allow clearance for utility lines, sidewalks and driveways, below-ground pipes and power lines, and property lines. The planting site should be prepared properly; soil quality and the amount of sunlight available can affect tree species differently. Taking the right steps before planting will help to ensure healthy trees for generations to come.

For more information on acceptable pruning methods and topping visit http://www.treesaregood.org/. 

Source:  International Society of Arboriculture