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Topping is perhaps the most harmful tree pruning practice known.
Yet, despite more than 25 years of literature and seminars
explaining its harmful effects, topping remains a common practice.
This brochure explains why topping is not an acceptable pruning
technique and offers better alternatives.
What is Topping?
Topping is the indiscriminate cutting 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."
The most common reason given for topping is to reduce the size
of a tree. Often homeowners feel that their trees have become too
large for their property. People fear that tall trees may pose a
hazard. Topping, however, is not a viable method of height
reduction and certainly does not reduce the hazard. In fact,
topping will make a tree more hazardous in the long term.
Topping Stresses Trees
Topping often removes 50-100% of the leaf-bearing crown of a
tree. Since the leaves are the food factories of a tree, this can
temporarily starve a tree. The severity of the pruning triggers a
sort of survival mechanism. The tree activates latent buds forcing
the rapid growth of multiple shoots below each cut. The tree
needs to put out a new crop of leaves as soon as possible. If a
tree does not have the stored energy reserves to do this, it will be
seriously weakened and may die.
A stressed tree is more vulnerable to insect and disease
infestations. Large, open pruning wounds expose the sapwood
and heartwood to attacks. The tree may lack sufficient energy to
chemically defend the wounds against invasion, and some insects
are actually to the chemical signals trees release.
Topping Causes Decay
The preferred location to make a pruning cut is just beyond the
branch collar at the branch's point of attachment. The tree is
biologically equipped to close such a wound, provided the tree is
healthy enough and the wound is not too large. Cuts made along a
limb between lateral branches create stubs with wounds that the
tree may not be able to close. The exposed wood tissues begin to
decay. Normally, a tree will "wall off" or compartmentalize the
decaying tissues, but few trees can defend the multiple severe
wounds caused by topping. The decay organisms are given a free
path to move down through the branches.
Topping Can Lead to Sunburn
Branches within a tree's crown produce thousands of leaves to
absorb sunlight. When the leaves are removed, the remaining
branches and trunk are suddenly exposed to high levels of light
and heat. The result may be sunburn of the tissues beneath the
bark. This can lead to cankers, bark splitting, and death of some
branches.
Topping Creates Hazards
The survival mechanism that causes a tree to produce multiple
shoots below each topping cut comes at great expense to the
tree. These shoots develop from buds near the surface of the old
branches. Unlike normal branches that develop in a socket of
overlapping wood tissues, these new shoots are anchored only in
the outermost layers of the parent branches.
The new shoots grow very quickly, as much as 20 feet in one year,
in some species. Unfortunately, the shoots are very prone to
breaking, especially during windy conditions. The irony is that
while the goal was to reduce the tree's height to make it safer, it
has been made more hazardous than before.
Topping Makes Trees Ugly
The natural branching structure of a tree is a biological wonder.
Trees form a variety of shapes and growth habits, all with the same
goal of presenting their leaves to the sun. Topping removes the
ends of the branches, often leaving ugly stubs. Topping destroys
the natural form of a tree.
Without the leaves (up to 6 months of the year in temperate
climates) a topped tree appears disfigured and mutilated. With the
leaves, it is a dense ball of foliage, lacking its simple grace. A tree
that has been topped can never fully regain its natural form.
Topping is Expensive
The cost of topping a tree is not limited to what the perpetrator is
paid. If the tree survives, it will require pruning again within a few
years. It will either need to be reduced again or storm damage will
have to be cleaned up. If the tree dies, it will have to be removed.
Topping is a high maintenance pruning practice, and there are
some hidden costs of topping. One is the reduction in property
value. Healthy, well maintained trees can add 10-20% to the value
of a property. Disfigured, topped trees are considered an
impending expense.
Another potential cost of topped trees is the potential liability.
Topped trees are prone to breaking and can be hazardous. Since
topping is considered to be an unacceptable pruning practice, any
damage caused by branch failure of a topped tree may lead to a
finding of negligence in a court of law.
Alternatives to Topping
There are times when a tree must be reduced in height or spread.
Providing clearance for utility lines is an example. There are
recommended techniques for doing this. If practical, branches
should be removed back to their point of origin. If a branch must
be shortened, it should be cut back to a lateral that is large
enough to assume the terminal role. A rule of thumb for this is to
cut back to a lateral that is at least 1/3 the diameter of the limb
being removed.
This method of branch reduction helps to preserve the natural
form of the tree. However, if large cuts are involved, the tree may
not be able to close over and compartmentalize the wounds.
Sometimes the best solution is to remove the tree and replace it
with a species that is more appropriate for the site.
Hiring an Arborist
Pruning large trees can be dangerous. If pruning involves working
above the ground or using power equipment, it is best to hire a
professional arborist. An arborist can determine what type of
pruning is necessary to improve the health, appearance, and
safety of your trees. A professional arborist can provide the
services of a trained crew, with all of the required safety
equipment and liability insurance.
There are a variety of things to consider when selecting an
arborist:
• Membership in professional organizations such as the
International Society of Arboriculture (ISA), the Tree Care Industry
Association (TCIA), or the American Society of Consulting Arborists
(ASCA).
• Certification through the ISA Certified Arborist program.
• Proof of insurance.
• A list of references (Don't hesitate to check.)
• Avoid using the services of any tree company that:
- Advertises topping as a service provided. Knowledgeable
arborists know that topping is harmful to trees and is not an
accepted practice.
- Uses tree climbing spikes to climb trees that are being pruned.
Climbing spikes can damage trees, and their use should be limited
to trees that are being removed.
For Additional Information
This brochure is one in a series published by the International
Society of Arboriculture as part of its Consumer Information
Program.
Why Hire an Arborist
Tree Benefits
Tree Values
Tree Selection
Buying High Quality Trees
Avoiding Tree & Utility Conflicts
New Tree Planting
Mature Tree Care
Plant Health Care
Trees and Turf
Proper Mulching Techniques
Pruning Young Trees
Pruning Mature Trees
Why Topping Hurts Trees
Insect & Disease Problems
Avoiding Tree Damage During Construction
Treatment of Trees Damaged by Construction
