What to Spray for Moss on Tree Bark

Copper Sprays

• Traditionally, copper fungicides offer relief when moss takes over your tree bark. Late winter to early spring, while your trees themselves are dormant, is a good time frame to apply the fungicide. Always check with your county extension office for a list of currently approved fungicides, so you comply with state law. Copper fungicides wash off naturally when rain falls and work best when they get a heavy rain after application.

Less Toxic Moss Killers

• Soap-based moss killers do less harm to the environment than copper fungicides, but are also newer and have been studied less. Made with potassium-based salts of fatty acids, they do biodegrade and are nontoxic, making them safe to apply in homes where children or pets play in the yard. Acidic moss killers, made from citric and acetic acids, also offer nontoxic moss removal. They can discolor wood, however, so aren't a suitable choice for tree bark.

What Not to Use

• Table salt won't kill the moss, despite a myth suggesting the converse. Products that contain iron sulfate and zinc can harm trees and plants, so should not be used for this purpose. While you can blast moss off surfaces with a pressure spray, this isn't recommended for removing it from tree bark. The high pressure can damage your tree.

Considerations

• While you can't say the same for roof moss, moss does not harm your tree bark. Leaving it alone is the most eco-friendly choice. You can create a less appealing habitat by pruning your trees so light and sun pierce the canopy. This naturally dries out the bark, making it a less inviting place for moss. Over time, your moss can die out and disappear.