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Topping
Hurts Trees
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
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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. |
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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.
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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. |
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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.Ê 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.
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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.
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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.
Developed by
the International Society of Arboriculture (ISA), a non-profit organization
supporting tree care research around the world and is dedicated to the
care and preservation of shade and ornamental trees. For further information,
contact: ISA, P.O. Box 3129, Champaign, IL 61826-3129, USA. E-mail inquires:
isa@isa-arbor.com © 1995 International
Society of Arboriculture. UPDATED JULY 2003. Back
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