Grey lichen-like growth on gingko bark and birch bark

(Question)

Gingko tree is planted near Lake Ontario in a fairly exposed location. It has been there for 10 years. This year, grey lichen-like, roundish growths have appeared on trunk and lower branches. None of the leaves on the lower branches have fully developed: they are tiny and not fully formed. The same phenomenon has appeared on the nearby birch clump, but has not affected leaf development. Do you know what this is? How does one go about removing it? It is very firmly attached to the bark. Will growth on the lower branches recover? Many thanks.

(Answer)

You may well have lichen growing on your trees. Lichen will develop in humid, damp, still conditions.  They are not harmful at all to the plant but they may be an indication of poor plant vigour.  They are more common on slow growing plants or older plants that are no longer growing at a vigorous rate.  The side of a tree facing the rain and prevailing wind will often be affected by moisture loving lichens.

Lichens can be controlled by improving air circulation through the pruning of overcrowded branches and cutting back any overhanging foliage.  However, the lichens as well as the poorly developed lower leaves on the gingko suggest some decline in the plant.  Has there been any environmental change in the area that is having a detrimental affect on your tree?  For example, as you’ve noted the trees are growing close to Lake Ontario, is there any chance the trees have been water logged recently?  Roots must have oxygen to live. Oxygen exists in the soil in tiny spaces between the soil particles.  If these spaces fill with water, there is no room for oxygen and the plant will suffocate.  Once the root cause is determined, corrective action will restore your gingko to more vigorous growth.

As the gingko regains vigour, the spread of lichen may slow but existing lichen will remain. Removal of lichen through scrubbing or the use of fungicides is not recommended as you may inadvertently damage the tree.

The link below provides more information on lichens and can help you confirm that the growths you are seeing on your trees are indeed lichens.  If you decide they are not lichens, please send us another request with a picture so we can consider alternatives.

Tree-Dwelling Lichen

https://njaes.rutgers.edu/pubs/fs1205/