An Immediate Threat
Hazard trees are trees that pose an immediate threat to people or property. If a land owner has been told by an arborist that a tree on their property is a hazard, from that point forward, the owner is legally liable for any injuries or damage unless they take action right away to remove the hazard. Once an arborist is called in to determine if a tree is a hazard, their responsibility as an arborist is to notify someone what action should be taken. Even if a tree is an immediate threat, it may not fall or break apart right away. Taking quick action can prevent costly damage.
How do you know if a tree is a hazard? Call in a certified arborist. Arborists have specific evaluation criteria to determine if a tree is unsound. A potentially dangerous tree is a legal issue. Being an arborist doesn’t require a college degree like a forester, but it does require very specific knowledge about tree structure and health. You can find an arborist using a tool available at the web site for the International Society of Arboriculture. They provide certification credentials for arborists and verification of certification for clients.
Deciding if you need to call in an arborist often involves common sense, but sometimes the threat is less obvious. This photo illustrates a tree that is clearly an immediate threat to people and property, but when you see a street tree with roots oozing out over the curb or the sidewalk, the tree may appear perfectly healthy above the ground. The roots are attempting to compensate for a very bad planting situation and an unstable, top-heavy crown. Healthy, stable trees can be hazards, too. A perfectly healthy tree becomes a hazard when it is planted too close to the edge of a high-speed highway, because not everyone stays on the paved travel lanes! When in doubt, call an arborist.
Just because a tree is damaged and dying doesn’t make it a hazard tree. A little, declining Dogwood can’t survive for long, but if it falls, nobody will be hurt. No harm, no hazard!
The following is by no means a definitive list of what is typical for an unstable tree, but it may help you a course of action. Strategic pruning can sometimes correct a hazard tree to make it sound. The potential avoidance of liability justification for hiring an expert for your tree evaluation and pruning job.
• The tree leans more than a few degrees
• The tree roots are climbing out and over a sidewalk
• The tree is dropping large limbs in an area with pedestrians
• The tree roots are exposed
• The tree has stopped growing, as evidenced by fungus and moss growing on the trunk or limbs
• The tree is covered with an invasive plant
• The tree has Resurrection Ferns growing along deteriorating limbs
• The tree has no dominant central leader and obvious dual or triple dominant trunks that are causing an occluded trunk structure
• The tree is hanging over a house or building
• The tree has a lot of crossing limbs that are touching each other