Tree Biology, Identification, and Growth Response Relevant to Utility Pruning
This domain tests tree biology as it affects utility pruning decisions: how trees grow, defend wounds, and respond to removal. The exam wants cause-and-effect reasoning, not vocabulary alone.
Core rules and concepts
- Trees compartmentalize decay through CODIT: chemical and anatomical boundaries slow the spread of fungi and decay.
- The branch collar and branch bark ridge are visible protection zones; a proper cut removes the branch without cutting into the collar.
- Auxin from terminal shoots suppresses lateral buds (apical dominance); removing terminals can release epicormic sprouts.
- Leaves produce photosynthate; heavy pruning reduces energy reserves and root growth, and a changed root-to-shoot ratio can trigger sprouting.
- Wound size, species, vigor, timing, and decay fungi affect response; large flush cuts are more likely to decay than smaller collar cuts.
Worked example
A 10-inch limb is cut flush to the trunk. The cut removes the branch collar and creates a large wound; decay fungi can enter and the tree has less boundary tissue. A proper cut just outside the collar leaves the protection zone and a smaller wound.
Traps that cost marks
Believing wound paint prevents decay; assuming topping invigorates a tree; cutting into the collar for a “clean” look; and expecting all species to sprout or compartmentalize the same way.