Thanks, @prydefoltz! Yes, those are the same berries. They have long vines close to the ground that run a long ways. Some showed up a few years ago, on their own, under my Blue Spruce tree. Now they have a big patch that is spreading -- up into the tree, too! I'm glad you know their flavor -- it is more intense than the big Himalayan blackberries.
American Elm leaves are in my top 5 favorite tree leaves to eat. They are so much bigger than other kinds of elms and they stay tender for a longer time. I think because they put off so much shade. I'm fortunate to live near a giant one. In their native habitat back East, they are mostly gone from Dutch Elm disease.
That is a shame. I do hope they begin a replanting programe.