ISA Certified Arborist Practice Exam Prep – Practice Test & Study Guide

Excessive tree pruning primarily causes tree stress, which can have significant negative effects on the tree's health and growth. When a tree is pruned too much, it may lose a substantial amount of foliage which is critical for photosynthesis. This loss can weaken the tree, making it more susceptible to diseases, pests, and environmental stressors such as drought and extreme temperatures. Additionally, excessive pruning can disrupt the tree's natural structure, potentially leading to structural instability.

While some pruning is beneficial for improving shape, air circulation, and light penetration, these advantages can be overshadowed by the detrimental impact of stressing the tree beyond its capacity to recover. Finding a balance in pruning practices is essential to ensure the health and longevity of the tree.