Identifying Hazardous Trees by 917mMF

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									  Identifying Hazardous Trees

Robert Bardon, Ph.D., RF., Cert. F.
Extension Forestry Specialist

North Carolina
Cooperative Extension Service
NORTH CAROLINA STATE UNIVERSITY
Recognizing tree hazards
• What is a hazard tree?
  – has a structural defect that may cause the tree or a
    portion of the tree to fall
  – has a “target” with in
    the falling distance
    of the tree or portion
    of the tree
      • targets include
        people, vehicles,
        homes, or other
        structures
  Looking for hazardous
       conditions
• Inspect
  systematically
  – crown
  – trunk
  – root zone
Examine the top and crown

•   Which species of tree is it?
•   What’s the tree’s history?
•   Is the tree dead or dying?
•   Are there dead limbs?
•   Do some branches cross or rub?
•   How vigorous is the Tree?
          Tree species

• Some trees are more brittle than
  others
  – bradford pear, willow, silver maple
  – check with city to see if ordinance
    prohibits any species
  – plant brittle species only in open area
  – avoid locating play areas and patios
    beneath these trees
            Tree history
• Past events warn
  of potential trouble
  – previous topped trees
    or storm-damaged
    limbs result in weak
    regrowth
  – unexplained loss of
    large limbs may be sign
    of internal damage
   Dead and dying trees

• should be
  removed
  promptly
• extremely
  dangerous to
  remove
• use an expert
               Dead Limbs
• accident waiting
  to happen
  – widow maker
  – may fall on calm
    days or if tree
    bumped
• larger than 1”
  diameter require
  prompt action
Crossed or rubbing branches
• lead to weak
  spots
• opening for
  pest and
  pathogens
• remove as
  soon as
  spotted
              Tree vigor
• compare to
  other trees of
  like size and
  location
• look at
  – amount of leaf
    cover
  – leaf size
  – leaf color
  – leaf condition
        Check the trunk
• watch for forked
  trunks
  – sign of potential
    weakness
     • cable or braces
       are used in
       larger trees to
       strengthen the
       fork
  – prone to infection
  – early pruning can
    prevent problems
       Inspecting the trunk

• what about balance?
  – removing all the crown from
    one side of a tree may cause
    the tree to be off balanced
  – leaning trees are more of a
    hazard than those growing
    vertically
      • any sudden lean indicates
        breakage or weakening of
        support roots and should
        be remove immediately
       Inspecting the trunk

• look for signs of
  decay
  – signs of internal
    decay
     • cavities,
       disfigurations
       (cankers), fungal
       fruiting bodies
       (conks)
                                 Inspecting the trunk
  • cavity trees
                                 12
      Thickness of sound outer




                                 10
                                       relatively safe
           wood (inches)




                                  8
                                  6
                                  4
                                                                                                    Danger
                                  2
                                  0
                                       16                        24                       32                        40                       48
                                                  Bole diameter inside bark (inches)

Figure based on research by US Forest Service on pine from Tree City USA Bulletin No. 15. Ed. James R. Fazio. National Arbor Day Foundation, Nebraska City, NE. 8 pp.
          Inspecting the trunk

• wounds and cracks
  – opening for decay
  – examine regularly
• two vertical cracks
  appearing on
  opposite side of
  trunk
  – sign of root injury or
    breakage
         Don’t forget the roots

• root decay
  – difficult to detect
  – major cause
      • construction
      • trenching
  – look for
      • mushrooms on or
        near the base of
        the tree
      • sudden shift of
        tree or large
        cracks in the
        ground

								
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