I have two of these plants side by side. They die back completely in the winter and new growth emerges in the spring. They are over 3 feet tall. I am sure that they have been here many many years (NH,USA Zone 4-5) . I have tried with no luck through neighbors and the internet. I cannot match the leaves. They look very similar to so many things and I personally am new to gardening. Any help would be greatly appreciated. Thank you so much.