The way I attempt to identify a plant, peony or other, is to really look at the plant and take pictures of things like the way the leaves appear. Are they big with dimples in the leaves, or serrated on the ends. Does the flower stand above the leaves or at or below leaf level. How many petals does it normally have. If it has seed bearing structure or not. If it has and you let them develop are seeds produced or an empty pod. How are the leaves attached to the stem. Is there 1 flower a stem or multiple flowers on a stem. Although color and shape is varible I tour as many nurseries or public gardens and attempt to match with a photo, either from my mind or a picture.

Having friend who grow many peonies I am lucky but if you start by making a check list of what your plant has then you can compare to other peonies. There are several places in Michigan and surrounding areas that are setting up peony gardens. University of Michigan is one of the places, sorry can not remember which campus.

See if you can get on lend for you at your local library several of the American Peony Society Books concentrating on the ones with lists of historic peonies before about 1900. I like James Boyd's book dated 1928 but it has been reprinted. Make a list of possibles and then locate plants to compare with your plant. Many of the older cultivars can be located in Canada so look at what is available at nurseries there.

One of the things that keep many from finding the name's is that over time plants can and will mutate. Each period of time people's tastes have changed and each period would have selected the section's of the plant to pass on that fit their taste.

Finding the actual name will be hard however I find it a nice way to spend a winter evening. You can look at all the picture's on Carsten Burkhart's site to see if you can find something similar. However his site will make you start your own collection Good luck on your search.

Here is a link that might be useful: Carsten Burkhart's peony pictures