How Trees Become Hazardous: Number 3 - Improper Pruning
Tree pruning is both an art and a science, and quite frankly, some people flunked both of those subjects. Flush cuts (picture at left) and excessive pruning are types of mistakes that lead to tree decline and death. Cutting the branch too close removes hormones that the tree needs to seal off the pruning cut.  An improperly pruned tree is subject to insect and disease problems and decay formation.

How Trees Become Hazardous: Number 2 – Topping
Topping, the indiscriminate removal of much of a tree’s canopy, is a sure-fire way to create hazardous trees. Topping violates most commonly accepted methods of proper pruning; it is an assault on the health and beauty of your tree, and a topped tree is much more likely to break apart during a storm than a tree with a natural growth pattern.

And the Number 1 Way Trees Become Hazardous: Construction Damage
Building a new home or an addition, putting in a new driveway or sidewalk, or trenching for utilities are all common construction activities that can put trees at risk. Severing roots, changing the grade of the ground, and other root zone incursions usually lead to the decline and death of mature trees. This picture of a new home (left) being build illustrates a feeble attempt to put a fence around the tree in hopes of saving it.  In this case, it was too little, too late.  Although this damage sometimes doesn’t appear until several years after construction, damage to tree roots is the number one killer of trees in the home landscape.

A final thought: What you do to keep a tree healthy today may prevent it from becoming a hazardous tree tomorrow. So now that you know what it takes to make trees hazardous, you also know what it takes to keep them healthy and safe. The next four modules cover various aspects of tree care in greater detail, and module 6 contains links to additional resources you can use to prevent hazardous trees.