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.
What is Topping?
Topping is the indiscriminate cutting back of tree branches
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 the 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 often removes 50-100% of the leaf-bearing crown of a
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 attack. The tree
may lack sufficient energy to chemically "defend" the
wounds against invasion. Some insects are actually attracted to
stressed trees by chemical signals.
preferred location to make a pruning cut is just beyond the branch
collar at the branch point of attachment. The tree is biologically
equipped to close such a wound provided 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 great path to move down through the branches.
Lead to Sunburn
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.
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 only anchored 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.
The cost of topping a tree is not limited to what the perpetrator
is paid. If the tree survives,
it will require pruning again with 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.There are some
hidden costs to 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.
are recommended techniques as alternatives to topping. If practical,
branches should be removed back to the their point of origin. If
a branch must be shortened, it should be cut back to a lateral branch
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 1/3rd the
diameter of the limb being removed. This should be done in an arc
across the crown of the tree to avoid flat topping. Avoid using
the services of any tree company that advertises and/or promotes
topping as a service.