A tree failure occurs when a tree or large part of a tree breaks and falls.  Hazard Tree Management deals in
probabilities of failure rather than certainties.  Age, species (especially rooting and branching characteristics), site, and condition all influence the relative hazard of the tree.  A high probability of failure does not make a tree a hazard; there also must be a “target” that could be damaged or injured if the tree fails.

Trees become a potential hazard when there is a target.  A target is a structure, vehicle or a person that would
be struck by a falling tree or its parts.  The target directly influences the degree of hazard.  Consider the differences
among a tree falling on a fence, a house or a person.  A tree leaning over the bedroom is most hazardous. Trees near high-use areas are more of a risk than those near infrequently visited areas, as the probability of a person being hit is

Tree age is important in hazard tree management.  Every tree species has an inherent life span.  Some trees inherently live longer than others.  Risk of failure increases with age.

A word about your liability.  If you have a hazardous tree, you may be responsible for any damage it causes if it
falls.  If a tree in your yard fails and damages your neighbor’s property, and you have no prior knowledge of its condition as a hazard tree, your neighbor’s general policy may cover the damages.  This determination however, may be disputed.  Documenting the condition of your trees can be important in case of litigation involving the failure of a tree.

This elm tree was completely dead, and posed a risk to houses and vehicles driving down the road.

This elm tree was completely dead. It posed a risk to houses and vehicles driving down the road.