I swear every single garden I saw while I was there had amazing sized peonies--even a few I saw planted out near the sidewalks in front of houses with no other gardens around! I think I actually took a few pics as I was walking up to one of the gardens Tracey suggested--I swear I'll get those pics posted eventually!
Found one of those--not in a special garden area but just in front of a nice, well kept house. Not a lot of garden other than these peonies but both the shrubs and the flowers were enormous! WI certainly has the climate to grow peonies!