What aspect is important for maintaining a healthy tree structure?

Maintaining dominant leaders and strong unions is critical for healthy tree structure because it ensures that the tree grows with a strong, stable form that can withstand environmental stresses. A dominant leader is the primary upwards-growing stem of the tree, and its presence helps to promote a well-defined scaffold structure, which is essential for both aesthetic value and structural integrity. Strong unions, where branches or limbs meet the trunk, are necessary to prevent weak points that could lead to branch failure.

Regularly pruning roots can disrupt the tree's anchoring system and nutrient absorption capabilities, while avoiding any pruning can lead to overcrowding and structural deficiencies. Reducing soil exposure does not contribute directly to the structural integrity of the tree and may also result in other issues related to root health and moisture retention. Thus, focusing on maintaining dominant leaders and strong unions is the best practice for supporting a healthy tree structure.