Well, I can't help, because I am also in Zone 5, near Chicago, and having a very similiar crispy brown edge problem.

I bought a Yagumo in June, also in a 1 gallon pot. I had it in the back yard in the pot, thinking I would plant in in partial shade, which is what the tag on it says to do. The nurseryman advised to put it in full sun to get the best blooms. So I put it in the front yard and amended the soil with lots of compost. I watered diligently, knowing that the root system would be essential.

Well, it has been hot, but the other plants around it, the sunlovers - salvia and coneflowers, are doing great.

So, are we to think that perhaps it should have a little less sun? The only thing the nurseryman told me when I called him about the brown edges, is that I should add some mulch (2 -3 inches) to keep the moisture in. He also recommended to only water it at the bottom, not to let the sprinkler or the hose get the leaves wet.

So I know I am not much help, but what do you think?
Anyone with any recommendations?

I went back to the Peony Forum and found a previous thread on tree peony planting shock. Lots of good information there - especially about the part shade/ full sun concern. Since my plant is still showing new growth, and many leaves are turning brown around the edges, I think everything is going to be okay.

Take a look at the previous thread - all particpants in zone 4- -5-6.

Planting in the heat of summer is a shock as the plant tries to extend feeder roots into native soil and supply as much moisture as is being transpired through the foliage due to a suddenly hot sun. Transplanting is always less stressful if done in the spring or fall. Al