Depending on the size of your root and the conditions it grows in, it may flower next spring. If not, then most likely the following year.

I have a few that I planted in my bed the spring before last and they are both finally increasing in stems and have several buds(never before had buds or flowered). Both were potted plants when I got them. One of them(Karl Rosenfield) only looks like 3 of it's buds are going to possibly bloom, the rest are pea size and haven't grown in weeks. The other has probably at least 10 buds that will *hopefully* bloom... Not sure why the difference, but I just hope it continues growing over the next few years.

Some of the potted peonies are planted too deep in the container. Unless you brushed all of the dirt off then planted, it is too deep.