Can Cause Hazardous Defects in Trees
failure is a major cause of residential property damage, as
well as the leading cause of power outages nationwide. An
ice storm can overload all the branches on a tree, a hurricane
or high wind can blow down a tree if its roots are restricted,
or a cracked tree can fail under its own weight.
"Homeowners worried about trees falling and damaging
property should call a professional arborist in for an inspection,"
advises Peter Gerstenberger, senior advisor for safety, standards
and compliance with the Tree Care Industry Association.
Gerstenberger notes that trees are designed to withstand storms,
but all trees can fail ‚ and defective trees fail sooner than
healthy trees. A sound tree becomes potentially dangerous
when the treeís woody structure is weakened by one or more
defects. During storms, pre-existing defects predispose trees
"To a professional arborist," notes Gerstenberger,
"defects are detectable signs that a tree has an increased
potential to fail." Broadly defined, there are seven
categories of defect: decayed wood, cracks, root problems,
weak branch unions, cankers, poor tree architecture, and dead
trees, tops or branches.
Healthy, well-maintained trees growing on suitable sites will
be able to minimize the extent of decay and other defects.
Trees that are stressed have reduced energy reserves, and
therefore, have less ability to deal with wounds and the ensuing
Most urban trees survive on construction-altered soils that
may be compacted, poorly drained, high in clay, sand, or gravel,
very alkaline or littered with construction debris. Additionally,
many urban trees are subjected to chemicals such as deicing
salts, herbicides and fertilizers commonly used in landscape
maintenance. Poor tree maintenance is another contributor
to stress. These cumulative stresses all take a toll on tree
vitality and structural integrity, increasing the risk of
All defective trees cannot be detected, corrected or eliminated.
Although a professional arborist can readily recognize most
defects, there are root problems and some internal defects
that are hidden. These trees may require in-depth assessments
and specialized diagnostic tools. Homeowners should also keep
in mind that defects change with time. A tree that looked
fine three years ago may have severe problems today. By doing
regular inspections arborists can successfully manage the
risk of tree failure.
Advanced decay and cavities, results in less structural strength
and reduced stability. Indicators of advanced decay are rot
ten wood, fungal fruiting bodies, cavities, holes, open cracks
or bulges in the wood. Decayed wood is the result of the long-term
interaction between a tree and decay-causing fungi. Wood decay
is an internal process with just a few external indications,
such as mushrooms, conks, rot ten or punky wood, cavities,
hollows, holes, inrolled cracks, and bulges in the wood.
The undecayed layer surrounding the decay column is called
the shell. If the shell thickness is thin relative to the
size of the tree, the shell is likely to fracture causing
the tree to fail. A tree can have internal decay and an opening
and still be structurally sound provided that the shell is
thick enough and the opening is not too wide.
If a tree is repeatedly wounded by the presence of inrolled
cracks, included bark, canker-rot fungi, or equipment (mowers,
plows, and weed whips), decay occurs in every annual ring
of wood. These trees should be carefully inspected by a professional
arborist because they do not form a sound shell of wood. The
tree is likely to fail at or near the location of the crack
or wound because a large and ever-expanding column of decay
is present there. Again, a professional arborist can evaluate
shell thickness and opening width to help determine the treeís
potential for failure.
Visual assessment by a trained arborist of the extent of decay
can often be a reliable means of predicting potential risk.
However, invasive techniques may be needed to quantify the
thickness of the sound shell of wood in comparison to the
size of the tree. Use of a probe or another tool may be needed
to test several areas in order to find the location of the
thinnest shell of sound wood.
In-depth assessments, using specialized diagnostic tools,
may be warranted when additional information about the location
and ex tent of internal decay is critical to assessing the
probability of tree failure.
What can you do?
For additional information go to our web site at www.SY
VTREECARE.com and read about choosing a contractor and
references on the home page. With years of experience and
education, I am able to assess and detect most problems with
trees. However, if your problem exceeds my knowledge, we have
two consulting arborist and one botanist with college degrees
available for further consultation. Give us a call today for
all your tree care needs.
from Tree Care Industry Magazine.
For more information please contact your local tree care specialist.
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