Hazardous Tree Evaluation

Are my trees safe?

This is one the most common concerns of homeowners and for good reason.  In 2008 I pointed out a hazardous tree to one of my clients while doing other work on the property.  She declined to remove the tree, even with my adamant recommendation and warning that it wasn’t a matter of it was a matter of when.  Within 2 years the tree fell directly across the peak of the roof doing over $127,000 worth of damage of the house.

Industry guide lines call for two conditions necessary for a tree to be deemed hazardous.  It must have both some type of structural defect, and/or an obstacle of value below, which could be anything from a house, fence, shed, swimming pool, and other valuable trees and shrubs in the landscape.  A proper evaluation on any hazardous tree should include both the analysis of the structural defect and the potential to mitigate them by pruning or cabling and the value of potential obstacles underneath or nearby the tree.  A tree with a low probability of failure that is over a house or other valuable property may be considered more of a problem than a tree with a higher probability of failure but one that threatens only obstacles of low value.  Daniel will meet with you personally, evaluate the structure of your trees and advise you of the probabilities and possibilities for remedial treatment.  We can often reduce the potential of a tree failure to near zero with proper pruning and cabling of an otherwise serious situation.

Trees have evolved for millions of years; they are genetically programmed to reach for the sun.  It is highly unusual for trees to grow in the open in natural settings.  Trees are genetically trained to compete for sunlight in a crowded, therefore the condition that trees grow in, in many suburban settings are extremely unnatural; on the edge of driveways, sidewalks, streets, in the open.

These trees in particular require periodic pruning in order to lessen for potential storm damage.  However, many times, when pruning a tree it is not necessary to remove a large amount of mass.  We only need to take away the “straw that will break the camel’s back”.  Though some pruning guidelines say that a tree can be pruned up to 25% of the green leafy material can be removed during pruning.  Older and larger trees do not do well with such a heavy pruning.  Most of the time 5% to 10% is usually needed to significantly reduce storm failure.

What are the structural defects?

  • Decay at the base of trees is evidence of either defects in the trunk, open hollows, or the presents or the presents of mushrooms, which are the fruiting body of fungus; most trees can have up to 70% decay and still be considered structurally sound.  That means that a hollow tree, which is 3’ in diameter can have a 2’ hollow in the middle surrounded by 6” of sound wood and still be considered sound. (Diagram:  tube/pipe theory).
  • Vertical cracks and compression or tension cracks in large leaning trees
  • Uplifted root plates
  • Codominant stems with included bark
  • Deadwood