Tree peonies have been in cultivation for several millenia and there are more cultivars than you can shake a stick at and often very similar in appearance. ID'ing an unknown is just a guess at best :-))

The waiting to plant until fall notion is pretty much a myth. There is nothing magical about peonies that require a fall planting. And the care and planting conditions are exactly the same as for herbaceous peonies except that you do not want to cut back into any of the woody stems. In fact, I don't recommend any pruning or cutting back at all.

the powder mildew could very well be due to the plant being kept inside. These are not houseplants and are extremely hardy and indoor conditions could harbor lack of air circulation and humidity that would be encouraging to PM. And full sun is fine and is the preferred siting for any kind of peony.

@gardengal48 I see. That may be why the tag just says Tree Peony.

Hmm I only pruned it because I thought it will stopped the powdery mildew from infecting more leaves. So you don't think I should move it (or give it some shade) even though the new growth (small leaves) died too? I guess I will just let it be for now.

How deep did you plant it? Tree peonies are grafted onto herbaceous roots for the most part, the most common propagation method for them since they're slower growing. If you planted it the normal 2" below soil or even the same depth as the pot you'll probably want it deeper, less likely that the herbaceous root will sprout which can cause it to not grow tree peony roots. ESPECIALLY if the small leaves didn't look like the original tree peony leaves....And tree peonies can take more shade than herbaceous, actually might prefer a slightly shady spot in OK, at least during the summer. Gardengal is right about planting peonies in spring as well, bareroot or potted (potted can be planted anytime), not that big of a deal. They are best divided in fall though since they're spring blooming. They might require more shade and water that first spring/summer if planted in the spring since they didn't have the fall and winter to settle in. I typically put a patio chair over the potted ones I plant in the spring to provide shade for a while, keeps them from wilting so much. And it probably will look a bit more ragged than one that's more established for the rest of the summer but should be just fine next spring, just keep watering as needed the rest of the summer. As for pruning, removing a few leaves is fine, lots of people advise removing all of the leaves for tps in the late fall, just try not to remove any branches or you'll destroy any possible blooms for next spring.

@lizbest1 Hmm I only planted it to the same depth as the pot. You are right. It may have been from the herbaceous root instead. I can't really tell the difference between the leaves though. I tried to search on google to no avail.

Y'know I bought the tree peony thinking that it can take more sun than herbaceous ones. I may have to plant it somewhere else because it gets no shade throughout the day at its current location.

Tree peonies can take full sun, just if they're spring planted they might need more shade that first spring/summer--just like any newly transplanted perennial they need a bit of babying to settle in.

Reviving this post again.

My tree peony did not have any growth/leaves at all this year. What should I do?