Trees and Home Construction

Minimizing the impact of construction activity on trees

Bulletin 870-99

Physical Damage to Trees

Broken branches, scraped bark, and other wounds are common symptoms of the unplanned or careless use of equipment and other activities on construction sites. Physical damage to a tree can result in the tree's death (immediate or delayed) or in increased maintenance costs to ensure the tree's survival (e.g., pruning, fertilizing, and more). Certainly much of the physical damage to trees that occurs during construction can be prevented if contractors exercise care.

The first step in reducing physical damage to trees is to plan where construction equipment will enter and travel on the property. The effectiveness of this step in reducing damage may be dependent on the size and character of the property, but it should not be overlooked even on small properties. There is absolutely no reason a contractor should damage desirable trees simply because they were located on the most convenient path of entrance or travel when alternatives existed. Minimize the number of paths to the extent possible.

The most effective method of minimizing damage to trees to be retained on the property is to establish a tree protection zone around each tree or group of trees. The tree protection zone is an area around each tree or group of trees in which no construction activity of any kind is allowed. During construction, the boundary of the tree protection zone is clearly marked with some form of temporary fencing. The establishment of tree protection zones is critical to reducing many types of tree and site damage and is discussed in detail in the section dealing with soil compaction.

In some situations retained trees have branches that extend into the construction area or into an area where equipment or vehicles must travel. These branches should be removed before construction begins using proper pruning techniques (Figure 2). The use of pruning paint does not reduce insect or disease problems and thus is not recommended. A thin asphalt-based paint can be sprayed on if a darker colored surface is desired for cosmetic reasons.

Figure 2. Proper pruning protects the branch collar of a lateral branch when making the final cut in removing the branch. When removing a codominant leader, use the branch bark ridge to position the final cut.

In addition, contractors need to understand the importance and value placed on the trees. In some instances, homeowners and contractors agree in the construction contract that the contractor will pay a stated amount (determined beforehand by a qualified arborist and different for each tree) for each tree damaged. Some property owners have even posted the trees' value on each tree to help construction crews understand the tree's value to the finished project.

Trees damaged during construction need appropriate care to recover as quickly as possible. Broken or severely damaged branches should be properly pruned (Figure 2). Loose bark or wood should be removed from around wounds to hasten wound closure (Figure 3). Again, the use of pruning paint or wound dressing is not recommended except as a cosmetic treatment. Heavy tars, like loose bark, retain water and favor disease development.

Figure 3. Remove dead and loose bark to reduce hiding and overwintering sites for insects. Loose bark retains moisture and favors disease entry as well.

If there is a question about the potential of a tree to recover from injuries, or a question concerning a tree's stability, the tree or trees should be inspected by an International Society of Arboriculture Certified Arborist.1 Occasionally guying or cabling may be necessary to improve stability. Guying and cabling should only be done by a certified arborist and should be reinspected every three to five years to ensure that the system is still functional.