Identifying Tree Hazards
Larry Bartlett, Certified Arborist
There are many advantages to having mature trees around your
home. They provide shade in the summer and protection from icy
winds in the winter. Homes with mature trees are attractive to
prospective buyers. Sometimes they can provide a privacy screen
and buffer against street noise.
There are times, however, when trees, especially large
trees, can present a hidden danger to person and property. Just
because a tree has leaves doesn't mean it's healthy. A closer
inspection of the large trees on your property can prevent an
accident from happening at the most inconvenient time.
As an arborist called on to survey a property for tree
hazards, I follow a list of criteria that helps the customer to
decide if the tree(s) should be removed.
These are some of the conditions that I look for:
Location: Is the tree located in a high
risk area? A tree in the lawn area or lawn edge doesn't hold
the same priority as the tree over the house, wires, or
Vigor: The tree may have leaves, but how
much new growth tells a bigger story as tohow healthy the tree
is. Is the new growth on the tips, or are there trunk
suckers,which may indicate a history of injury to the tree?
Deadwood: Is there deadwood in the tree?
Deadwood in the center of the tree may just be an indication
that the tree is too thick and needs to be thinned. Deadwood in
thecrown of the tree is much more serious. That is an
indication of root damage or basal decay.
History: If a tree is showing the signs of
stress, I find out from the customer how old the house is, or
if there had been any construction in the vicinity of the tree.
A tree's root zone spreads far beyond the drip line of the
tree, and requires oxygen as well as water to function.
When heavy equipment is driven repeatedly over the active
root zone of the tree, there's a pretty good chance that a
percentage of that tree has been cut off. That percentage shows
up in the crown of the tree. Soil compaction is especially
common in new construction.
Trying to save the trees on a wooded lot is difficult when
building new homes. I usually recommend that all the trees in
the disturbed soil area be removed, and new trees planted in
prepared planting beds by design.
Decay: This is the most difficult to
diagnose. A tree may appear healthy with leaves and still
present a serious hazard in the form of decay. Decay is a
structural defect that can show up in the base of the tree or
in the large supporting branches of the crown.
An indication of decay might be broken off branches that are
not dead. Observing the tree in the wind, it would appear to
bob instead of sway. Sporadic deadwood of smaller branches may
also indicate unsound wood.
Weak forks: Also called co-dominant stems,
this is the most common structural defect in a shade tree. When
vertical stems grow side by side, or vigorous vertical stems
offshoot the trunk, the tree will easily split in half under a
load of heavy ice or just the right wind gust.
When the tree is small these limbs should be pruned out. If
the tree is large, a high strength cable support system can be
installed in the crown of the tree. The injury to the tree
isminimal, and if the tree is healthy it simply grows around
it. Cabling can extend the life of a mature tree for many
Tree pruning and
cabling services available in Derry, Windham, Londonderry,
Manchester, Bedford, Hudson,
Hollis and Nashua, New Hampshire.