How do structural defects in trees typically manifest?

Structural defects in trees often manifest through visible physical symptoms such as cracks, leaning, or irregular growth patterns. These symptoms indicate an underlying problem affecting the tree's stability and health. Cracks in the trunk or branches can suggest internal decay or weakness, while a leaning position often points to root failure or issues with structural integrity. These signs are crucial for assessing the risk a tree may pose, particularly in urban environments where trees are in close proximity to structures and people.

In contrast, the other options do not adequately describe how structural defects are typically observed. A lack of leaves and branches may result from multiple conditions, including environmental factors, but does not directly indicate structural integrity. The presence of pests, while potentially relevant to a tree's overall health, is not a primary indicator of structural defects. Finally, growing taller than usual does not specifically relate to structural issues, as height can be influenced by a variety of factors, including species growth rates and environmental conditions. Therefore, the clear manifestation of structural defects is best characterized by symptoms such as cracks and leaning.