This is YOUR year, Deb, I can just feel it! A little bulb fertilizer like Kousa recommends can't hurt. If yours was a seedling, actually grown from seeds dropped by your neighbor's tree peony, it could take that long to flower but I'm surprised at the size. Is it in a position that it could be getting fertilized with your lawn or anything too high in nitrogen? Have you ever seen any buds forming at all? I'm no where near an expert on tree peonies but your pics look like a healthy one that should be blooming soon.
Okay, before I finished this post I thought I'd do a quick search and came across this from Dave's Garden: It says it can take 5-9 years for P. Lutea to bloom from seed! Holy cow that's a long time to wait!
