What is the process of natural pruning primarily focused on?

The process of natural pruning is primarily focused on branch removal at nodes related to branch collars. This approach emphasizes the importance of making cuts at specific locations on the branches, known as nodes, where they connect to the parent branch or trunk (the branch collar).

When cuts are made at the branch collar, this location contains the necessary tissues that promote healing and callus formation, minimizing the risk of disease and decay. This method enhances the plant's natural defense mechanisms, allowing it to divert resources to healthier growth and overall vigor. It also helps maintain the structural integrity and balance of the tree by selectively removing branches that may conflict with others or are less productive.

The other options do not embody the principle of natural pruning as effectively. Selective thinning of foliage may contribute to overall health but doesn't directly reflect the focus on branch collar pruning. Complete removal of all branches is excessive and detrimental to the plant's health, while encouraging growth by cutting back focuses on promoting new growth rather than the health management inherent in natural pruning techniques.