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Recognizing Tree Hazards Trees provide
significant benefits to our homes and cities, but when trees fall and injure
people or damage property, they are liabilities. Taking care of tree hazards
makes your property safer and prolongs the life of the tree.
Trees are
an important part of our world. They offer a wide range of benefits to the
environment and provide tremendous beauty.
However, trees may be
dangerous. Trees or parts of trees may fall and cause injury to people or
damage to property. We call trees in such situations hazardous, to signify the
risk involved with their presence. While every tree has the potential to fall,
only a small number actually hit something or someone.
It is an owner's
responsibility to provide for the safety of trees on his or her property. This
brochure provides some tips for identifying the common defects associated with
tree hazards. However, evaluating the seriousness of these defects is best done
by a professional arborist. Regular tree care will help identify hazardous
trees and the risk they present. Once the hazard is recognized, steps may be
taken to reduce the likelihood of the tree falling and injuring someone.
Hazardous Trees and Utility Lines
Trees that fall into utility lines have additional serious
consequences. Not only can they injure people or property near the line, but
hitting a line may cause power outages, surges, fires, and other damage. Downed
lines still conducting electricity are especially dangerous. A tree with a
potential to fall into a utility line is a very serious situation.
Tree Hazard
Checklist Consider these questions:
| • |
Are there large
dead branches in the tree? |
| • |
Are there
detached branches hanging in the tree? |
| • |
Does the tree
have cavities or rotten wood along the trunk or in major branches? |
| • |
Are mushrooms
present at the base of the tree? |
| • |
Are there cracks
or splits in the trunk or where branches are attached? |
| • |
Have any branches
fallen from the tree? |
| • |
Have adjacent
trees fallen over or died? |
| • |
Has the trunk
developed a strong lean? |
| • |
Do many of the
major branches arise from one point on the trunk? |
| • |
Have the roots
been broken off, injured, or damaged by lowering the soil level, installing
pavement, repairing sidewalks, or digging trenches? |
| • |
Has the site
recently been changed by construction, raising the soil level, or installing
lawns? |
| • |
Have the leaves
prematurely developed an unusual color or size? |
| • |
Have trees in
adjacent wooded areas been removed? |
| • |
Has the tree been
topped or otherwise heavily pruned? |

Defects in Urban Trees The following are
defects or signs of possible defects in urban trees (see image above):
1. regrowth from
topping, line clearance, or other pruning 2.
electrical line adjacent to tree 3. broken or
partially attached branch 4. open cavity in trunk
or branch 5. dead or dying branches
6. branches arising from a single point on the
trunk 7. decay and rot present in old wounds
8. recent change in grade or soil level, or other
construction

Defects in Rural Trees The following are
defects or signs of possible defects in rural trees (see image above):
1. recent site construction, grading and tree
removal, clearing of forests for development 2.
previous tree failures in the local area 3. tree
leaning near a target 4. forked trunk; branches and
stems equal in size 5. wet areas with shallow soil
Managing Tree
Hazards An arborist can help you manage the trees on
your property and can provide treatments that may help make your tree safer,
reducing the risk associated with hazardous trees. An arborist familiar with
hazard tree evaluation may suggest one or more of the
following:
| • |
Remove the target.
While a home or a nearby power line cannot be moved, it is
possible to move picnic tables, cars, landscape features, or other possible
targets to prevent them from being hit by a falling tree. |
| • |
Prune the tree.
Remove the defective branches of the tree. Because
inappropriate pruning may weaken a tree, pruning work is best done by an ISA
Certified Arborist. |
| • |
Cable and brace the
tree. Provide physical support for weak branches and stems
to increase their strength and stability. |
| • |
Provide routine care.
Mature trees need routine care in the form of water, fertilizer
(in some cases), mulch, and pruning as dictated by the season and their
structure. |
| • |
Remove the tree.
Some hazardous trees are best removed. If possible, plant a new
tree in an appropriate place as a replacement. |
Recognizing
and reducing tree hazards not only increases the safety of your property and
that of your neighbors but also improve the tree's health and may increase its
longevity!
Ensuring
Quality Care for Your Tree Trees are assets to your
home and community and deserve the best possible care. If you answered "yes" to
any of the questions in the tree hazard checklist or see any of the defects
contained in the illustrations, your tree should be examined by an ISA
Certified Arborist. If your tree is located near a power line, contact your
local electrical utility.
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