I need help identifying this "volunteer" in a group of common lilacs, and also the interesting growths on its leaves. The growths are found all over the tree, and are firm and slightly "fuzzy." The tree gets mostly western sun.
Thank you again for providing this service.
We think that this looks most like some kind of Elm, and the things you are seeing on the leaves are called galls.
There are many types of leaf galls, which are just abnormal swelling of tissues. They are not of concern.
Here is more about them:http://extension.umd.edu/hgic/topics/shade-tree-galls
Search Elm galls and compare.