What causes the green mold on your red maple tree?

The green mold on your red maple tree is likely due to a type of algae or a lichen that thrives in moist, shaded environments. These organisms can grow on the bark and branches, particularly if the tree is stressed or has poor air circulation. While not harmful to the tree itself, the presence of mold can indicate underlying issues such as excess moisture or a lack of sunlight. It's important to monitor the tree's overall health and address any environmental factors contributing to the mold growth.