Republished with permission from Brian A. Kunkel, Extension Specialist, Ornamental IPM , University of Delaware Cooperative Extension at https://extension.udel.edu
We have seen lush growth of lichens and moss this season, mostly on understory trees and shrubs that are in partial shade. High humidity and adequate rainfall have supported the growth of lichens, which are symbiotic growths of fungi and algae together. Moss will most often grow in sites with low pH. Neither are pathogens, and will not harm trees and shrubs.