I had a lovely tree peony for a couple of years, but it seemed much too big for my small garden. I dug it up and gave it away to a friend.
Most tree peonies are grafted onto herbaceous peony root stalk and when I dug the peony, I must have left some of the original root stalk in the ground. Now, three years and one gift later, I have a really exquisite peony. It is a single peony coming from a piece of the original root stock. I think I like it better than the multi-petalled tree peony. Sometimes nature just makes good decisions for you!