What is "topping" and why is it bad?
According to the International Society of Arboriculture (ISA), "topping is the indiscriminate cutting back of tree branches to stubs or lateral branches that are not large enough to assume the terminal role. Other names for topping include 'heading,' 'tipping,' 'hat-racking,' and 'rounding over'." Topping violates nationally accepted standards for proper pruning and seriously injures trees.

Problems caused by topping:

Starvation. Good pruning practices rarely remove more than 1/3 of the crown, which does not seriously interfere with the ability of a tree's leafy crown to manufacture food. Topping removes so much of the crown that it upsets an older tree's well-developed crown to root ratio and temporarily cuts off its food-making ability. The tree goes into shock and readily produces new shoots.

Weak new growth. The branches that sprout following topping are much more weakly attached than a naturally developed branch. Rot at the severed end of the limb can make a bad situation even worse.

Rapid new growth. The goal of topping is usually to control the height and spread of a tree. However, it usually has exactly the opposite effect! After topping, trees vigorously re-sprout. The resulting sprouts are far more numerous than the normal new growth and they elongate so rapidly that the tree returns to its original height in a very short time.

Why do people top trees if it is so bad?

People top trees because it requires relatively little skill and time. All they need is a truck and chainsaw! It works out best for companies to top trees because it is quick and easy; since the growth will be back in 2-3 years, they have created more work for themselves in the future. If a company suggests topping, always get a second opinion. A good arborist will almost NEVER suggest topping.

Many homeowners have their trees topped when the trees reach heights they consider unsafe. They are afraid a strong wind will blow the trees down. What they fail to realize is that they are actually creating the very problems they are trying to avoid; if the tree survives, many weakly attached branches will just sprout back next year, usually higher and bushier than the original limbs. Thus, topping creates a more, not less, hazardous tree.

Some homeowners have their trees topped to preserve their views. However, a topped tree will sprout back higher and bushier than the original size. Unfortunately, what they fail to realize is that properly pruned trees can actually naturally frame their views and increase their property value.

So how can we get people to stop topping?

Topping is the most harmful tree practice known. However despite more than 20 years of research and studies documenting and explaining its harmful effects, topping remains a common practice. The only way we can stop topping is through education and outreach to property owners and tree care companies.

Property owners first need to understand why topping is bad and then stop requesting this service. Property owners who hire a tree care provider should specify "no topping" and request that their trees be pruned to ANSI A300 standards and by the International Society of Arboriculture guidelines. Most reputable tree care companies will not include "topping" in their advertisements or list of services, so stay away from companies that do.

The best way to find a qualified tree care company is to hire an ISA Certified Arborist. ISA arborists have demonstrated a minimum level of tree care knowledge and stay up to date on current research through continuing education. A good arborist rarely recommends topping, and should try to talk you out of it if you request to have a tree topped.

What are some alternatives to topping?

Plant the right tree in the right place. Carefully select the appropriate species before you plant a tree. Bear in mind the mature size of the tree and do not plant trees that will cause future conflicts with infrastructure, utilities, structures or views. Young trees should also be properly trained.

Prune properly to allow your trees to realize their full potential for health and beauty in the landscape. Proper pruning can remove excessive growth without the problems topping creates. If you have your trees properly pruned, you should not need to have them pruned again for 10-15 years; conversely, if you top your trees you may have to prune your trees every few years.

Enhance views by "windowing" or "crown raising." "Windowing" is defined as removing several branches symmetrically within an area of the tree. By carefully choosing which branches to cut, and making proper pruning cuts, you can leave a window in a tree that provides a fully framed view and also maintain the health of the tree. "Crown raising," or "skirting," is the removal of lower branches to open up a view. To maintain a healthy tree, do not remove more than 25 percent of the canopy of a tree at one time.

Remove dead, dying, diseased, crowded, weakly-attached, or low-vigor branches through "crown cleaning."

Consider "crown reduction" when a mature tree's height absolutely must be reduced, such as to correct utility line conflicts. Crown reduction is accomplished by removing larger branches at the top or side of the tree. Branches are removed by using proper pruning cuts above a lateral branch that will increase in size after cutting. This is the method that Clark Public Utilities uses to maintain their utility lines. Crown reduction is also known as "drop crotch pruning".

TREE TOPPING MYTHS:

The tree is too tall. This indicates either poor species selection, improper tree placement, or fear that the tree might be dangerous in storms.
Topping reduces the risk of storm damage. the reduction in height reduces risk temporarily, but as the tree regrows, it is structurally weaker and the risk becomes greater.
It produces a denser shade. The shade may be denser in a small area, but the overall shading potential is reduced.
It has to be topped because of power lines. Tree and power line conflicts may be resolved by proper species selection, better placement or different pruning technique. Remember: power line clearance benefits the lines, not the trees.

PROBLEMS CAUSED BY TOPPING

The balance between roots and crown is destroyed. Removal of too many branches and leaves can starve trees, Without foliage trees cannot make enough food to maintain growth and vigor.
Sunscald can occur. Bark tissues suddenly exposed to full sun may be burned and develop disease cankers.
Large stubs can't heal. Stubs are separated from food and water flow. As tissue dies, wounds don't seal, and decay may enter and spread to the trunk.
New growth  is weak. New sprouts are attached to the surface of stubs rather than being anchored from within former limbs.
Topping can create hazard. Storms do more damage because the new growth is weakly attached.
Topping disfigures trees. Topping alters trees' natural beauty and form.
Topping is only temporary. Trees will grow to their natural height. Rapid regrowth is nature's way of recovering from disasters, and frequent topping will be required to keep a tree under control.

Visit these great websites for more info on tree topping:
Plant Amnesty   International Society of Arboriculture   TLC for Trees