The answer to 'why is my retaining wall dead trees' is that there are several common causes for dead trees around a retaining wall. Improper soil drainage, root damage from wall construction, or the wall itself blocking sunlight and airflow can all lead to the trees declining and dying.
Symptoms include wilting, yellowing leaves, and the tree eventually dying off completely. To solve the issue, you'll need to address the root cause - whether that's improving drainage, adjusting the wall design, or replanting trees in a better location. For complex retaining wall problems, it's best to consult a professional landscaper who can properly diagnose and fix the issue.