What is the growth on my tree?
Usually mossy growth is not particularily causing the death of a tree. This could simply be a form of lichen which tends to grow on the north or shady sides of the trunk. But here’s something of note… If they are Russian Olive trees; sort of with a bluish green cast to the leaves; then unfortunately these trees donot have a long lifespan as compared to other native trees. You mentioned olive tree, but not the variety. My favorite woody trees and shrub book, by the way is written by Michael Dirr. It is the most informative plant book you could ever own. But it can be expensive, so try to buy it used from amazon.com if your a horticulture nut as myself. Actually I’m a landscape architect from the midwest. Hope this helps.
