Certified Arborist Practice Exam 2025 – Comprehensive All-in-One Guide to Master Your Certification!

The correct choice for establishing a single central leader or removing competing leaders is subordination. This type of cut involves selectively removing the more vigorous competing stems or branches, which allows the remaining central leader to take dominance. By doing this, the tree's overall structure is enhanced, promoting a more ideal form and reducing the risk of future structural issues associated with multiple leaders.

In contrast, heading cuts, which shorten a branch or stem, are typically used for maintenance and do not specifically address the issue of competing leaders. Thinning cuts remove foliage or branches without significantly shortening them, which can help improve air circulation and light penetration but does not directly resolve leader competition. Reduction cuts are primarily used to shorten a branch while maintaining its structural integrity and do not focus on establishing a single leader. Thus, subordination is the most effective option for achieving a desired tree form by promoting a single central leader.