Next to our birdbath a tree started growing. We replanted it to see what would happen. It is now healthy, growing, and we must move it to a permanent location. Problem: we have no idea what kind of tree, how big it will get, etc.  Right now it is approx 24 inches with several branches from the main part. The branches are covered in bark except where new growth is. It has alternate leaves with small double spikes at the joints. Leaves end in a point with a slight serrated edge. I do hope someone there has better luck in identifying than we have.