What is a threaded rod commonly used for in tree support?

A threaded rod is commonly used in tree support specifically to provide structural reinforcement to weak sections or crotches of a tree. This form of support helps in stabilizing branches that might be at risk of breaking due to weight, wind, or disease. By using threaded rods, arborists can effectively secure these vulnerable parts, allowing the tree to maintain its integrity and continue thriving.

The other options do not accurately describe the function of a threaded rod. Promoting growth in branches is typically achieved through other horticultural practices, not mechanical support. Enhancing a tree's resistance to pests usually involves treatment methods and pest control measures rather than physical support systems. Protecting a tree from lightning strikes is primarily managed through lightning protection systems, which involve different materials and techniques designed specifically for that purpose. Thus, the use of threaded rods focuses solely on providing mechanical support rather than influencing growth, pest resistance, or lightning protection.