New Tree Peony in a Pot

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?

I had bought one a few years ago and immediately planted it in a larger pot. Large enough for a specimen plant on the deck. However, I lost it over the winter and am expecting that it was because the plant had not had enough time to get it's roots established, plus, I am in zone 5 so it probably should be in the ground.

I don't remember about planting it. How deep.

Thanks Jnette. I intend to keep it in the garage during winter. What a shame about your plant.

I think they are pretty tough. I bought a TP that had been overwintered in a similarly sized pot by keeping it in a cold frame which gave it plenty of sunshine. They will live even if you can't completely cover the grafted area but an inch or so in the pot probably won't hurt. When you do plant it out, planting it deeply helps it to get established. That's just my opinion.

I think it just had not had time to get it's roots established before it got cold. I think in the colder climates they should be either in the ground or in a garage etc.

I've potted it up two inches deeper as that's all I could manage without disturbing the soil from the original pot. It looks handsome! It already bloomed at the nursery, so I hope to see it bloom next year.

It doesn't get too cold here, but the wind is freezing and can be powerful, so I'll keep it in the garage over winter. I may have to put one of those burlap bags around it in winter after I do plant it to prevent dieback.

Thank you for your replies!