Green moss thrives in areas with poor air circulation, high moisture and indirect sunlight. Whether on a cedar fence or a tree trunk, green moss can be unsightly, but because it draws its nutrients from the surrounding atmosphere, it poses no direct threat to trees or fences. Some even welcome green moss because it is a sign that there is no significant level of air pollution in the area. While these simple plants are quite easy to get rid of, to keep them from coming back you must change their growing conditions and vigilantly monitor new growth.
Wet the mossy area of the tree trunk and cedar fence with a hose.
Spray the tree trunk or cedar fence until it is thoroughly wet. Your cedar fence and most hardwood ornamental tree trunks can be sprayed with a soapy moss killer containing potassium salts of fatty acids, such as Safer Moss and Algae Killer. These sprays will effectively kill existing moss and inhibit new growth as well.
Leave the spray on the tree trunk and cedar fence for 10 minutes.
Brush the dead moss off the tree trunk and cedar fence with a soft push broom or brush.
Rinse the tree trunk and cedar fence off with water.
Prune the overhead branches. They are likely restricting the direct sunlight and air circulation that will keep green moss at bay. Prune any crossed, broken, small or damaged branches all the way back to the main branch.
Keep a look out for and immediately re-treat any moss regrowth.