I love my tree peonies, I have five plants, two pink, one white, and two yellow, one is very lemony and the other one is like orangy yellow with red centre. They are very easy to grow, the yellow ones and the white one I planted at the back, they are very tall, about 3ft, the pink ones in the front, they are not as tall as the back.
The flower does seed, they are big just like pea, they are black, I planted them but they take a long time to germinate, I think it is two years, so I got three more pink ones.
We should al try to grow them. Good luck.