Peonies: New Tree Peony in a Pot, 1 by poinget

poinget wrote:
Hello!

I just bought a tree peony called Koukamon. The tag says it's a 3 year grafted plant. I won't be able to plant it into the ground until next year; however, I think it needs to be moved from its 1 gal pot into a deeper one. The lady said I should plant it at the current soil line, but I have read I should plant it 4-6 inches above the graft to ensure the herbaceous nurse root doesn't sprout. The highest green marker is about 6 inches above the soil line shown in the pic. The grafted area seems to be visible or am I wrong?

Also, since I won't be planting it, how do you recommend I care for it over the winter?