One of the goals of structural pruning is to keep branches less than what diameter in relation to the trunk?

In the context of structural pruning, the goal is to maintain a healthy tree structure that promotes stability and strength as it matures. When considering the relationship between branch diameter and trunk diameter, it is recommended that branches should be less than half the diameter of the trunk. This guideline helps ensure that the tree remains balanced and that the weight of the branches does not place undue stress on the trunk, which can lead to structural weaknesses or failure.

When branches exceed half the trunk's diameter, they can create leverage that makes the tree more susceptible to damage from wind, snow, or ice. Therefore, maintaining branches at this proportion allows for better overall form, reducing the likelihood of branch breakage and promoting a healthier growth pattern. Keeping branches under this threshold is an important practice in arboriculture, especially for young trees that are being trained into a strong, sustainable form.