Tree Peony, Paeonia suffructicosa 'GODAISHU' (MOON WORLD)?
These are some of our most beautiful flowers in the garden. The flowers are very large with the biggest measuring about 6" when fully open. They open during the day and close at night so it's as if you get a new flower each day.
I bought several of these white tree peonies three years ago and I'm glad to say they've thrived wonderfully. The very large white flowers have crinkly petals sort of like crepe paper. Actually when I think about it it's more like wrinkled tissue paper. Anyway the inside base of the flower is dusky red and contrasting deep yellow stamens make the plant a head turner. There are many more interesting colors to choose from, yellows, reds, purple, pinks, some with single, double or multiple petals but I think I'm satisfied with these and don't have a need to look for more.
I like the herbaceous peonies too, but I don't like the fact that they fall over all too easily. You don't have to stake the tree peonies as the woody stems are quite strong.
Here's a great nursery website suggested by Entangled that has photos of 83 kinds of tree peonies!
Klehm's Song Sparrow Nursery