Unknown Tree #1

This tree grows wild in my back yard, Maine, Zone 4.
The area is shaded and often wet.
The trunk seems to only get as wide as about 3 inch wide. See mysterytree012
The tallest of these little trees is around 15-20 ft.
The shape of the leaves are interesting indeed.
I just snapped these shots (May 11) as the tree was sprouting tiny green flowers
That are now hanging down as tiny bells.