Why 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. Home owners often 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 to 100 percent of the
leaf-bearing crown of a tree. Because leaves are the food factories of a
tree, removing them 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 so, 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
attracted 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, which
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 quickly, as much as 20 feet in one
year, in some species. Unfortunately, the shoots are 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 leaves (up to 6 months of the year in temperate
climates), a topped tree appears disfigured and mutilated. With 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, with
some hidden costs. One is the reduction in property value. Healthy,
well-maintained trees can add 10 to 20 percent to the value of a
property. Disfigured, topped trees are considered an impending expense.
Another possible cost of topped trees is potential
liability. Topped trees are prone to breaking and can be hazardous.
Because topping is considered 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
Sometimes a tree must be reduced in height or spread.
Providing clearance for utility lines is an example. There are
recommended techniques for doing so. 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 is to cut back to a lateral that is at
least one-third 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 the type of
pruning that 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.
When selecting an arborist
- ask for proof of insurance.
- ask for a list of references, and don’t hesitate to check them.
- 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.
Source credit
International Society of Arboriculture
http://www.isa-arbor.com
