Look for a loss of leaves or discoloration of the leaves in the upper canopy when the tree is in bloom. Identify if there are large dead branches, or detached branches hanging in the tree. Cracks in the trunk or bark, and mushrooms at the base may be a sign of decline. Consult this online resource for additional information. If the tree is on your property, consult an arborist. If the tree is on City property, contact Parks Customer Service.