Will Moss on My Spruce Trees Harm Them?

Varieties

• There are nearly 23,000 different types of mosses likely to appear on trees such as spruce and other surfaces, according to the Reader's Digest Association's "1001 Hints & Tips for Your Garden." The presence of moss on trees is often viewed as an aesthetic element by many homeowners while others prefer to remove the fuzzy plants. This is a personal choice, however, and not recommended because the mosses are not harmful to the tree in any way.

Discouraging Moss Growth

• Mosses are more commonly seen on older spruce trees. Increasing the amount of direct light on the trees discourages moss growth. Also, trees that have poor air circulation are more prone to moss growth. You can increase air circulation by thinning the canopies of heavy trees. Spruces and other trees and shrubs in polluted urban areas rarely encounter moss growth.

Manual Removal

• Mosses are easy to remove manually by hand. However, this is a time and labor intensive strategy more suited for shrubs rather than larger-sized trees such as spruce. If you wish to hand remove the moss, the best time to do it is during winter. The tree is less likely to be damaged since it's in the dormant growth state. If physical removal is attempted during the active growth period of the tree, the newly growing buds are likely to be seriously damaged. Another option is to use a power washer to wash the moss off the tree. Do not attempt this on delicate plants. For spruce, the best time to attempt this method is also during winter.

Chemical Control

• The chemical control of moss on spruce is done with the use of copper sulfate or lime sulfur. Both products, however, are toxic and not available to homeowners. A professional tree care company needs to be hired for application. The Oregon State University Extension does not recommend chemicals for moss removal since moss plants do not parasitize the trees and because the effects of the chemical are generally short lived.