A couple of people have recently asked if the grey moss-like growth on the limbs and twigs of their trees and shrubs is the primary source of their decline.

Trees and shrubs often have this sporadic growth on limbs and branches called lichen. Lichens are very common occurrence in our landscapes. The unusual growth is a type of hardy algae that survives superficially on the plants bark and it is not a parasitic type plant feeding on the plant’s vascular system.

Lichens can also be found on non-living surfaces such as rock, tree stumps and even brick foundations. The spread of lichens is not the primary cause for the decline in growth or death of shrubs and trees. However, lichen development on trees or shrubs is associated with with poor growth or environmental stress of plants.

If practical, the lichen affected limbs or twigs can be pruned out to stimulate new growth. Plant vigor is the best way to control lichens. Poorly growing and declining plants often succumb to lichen growth during their decline. Unfortunately, pruning out lichens will not save a declining tree or shrub.

More information on lichens can be found at http://www.aces.edu/pubs/docs/A/ANR-0857/ANR-0857.pdf