The answer to 'why is my hedge dead trees' is that there are several common causes for a hedge to die, including disease, pests, improper planting or maintenance, and environmental stress. Symptoms may include wilting, discolored or dead leaves/needles, and dieback of branches. To address the problem, you'll need to identify the underlying cause and take appropriate action.
If the issue is due to disease, pests, or environmental factors like drought or frost, you may be able to save the hedge by pruning out affected areas, applying treatments, or adjusting growing conditions. However, if the hedge is beyond saving, it's best to remove and replace it. In either case, it's often best to consult a professional landscaper or arborist to properly diagnose and treat the problem.