Jase,

Some of my tree peonies are also looking a bit rough right now. All of the foliage is put on in the spring and by this time of the year it is getting a bit tired. If the tree peony is in its first year then I would assume that it is normal due to not having a lot of root structure yet. The leaves should stay somewhat green until your first hard frost.

You are in the Kansas City area. Hope to see you at the Heartland Peony Sales on October 1st. I know that there will be hundreds of tree peonies there for sale. You can find information on that sale at www.peonies.org/calendar.html

I wouldn't worry about it. My leaves look rough, but I give no extra water in a very dry spot and its been a dry year. The leaves will fall when they fall. The other thing is they tend to get fungal infections that can make the leaves unsightly. It isn't too harmful this late in the year, but clean up and destroy infected leaves to prevent the infection coming back stronger next year.