I have a grafted tree that I overwintered in the garage that I bought potted last Fall. I want to plant it now but I am wondering how deep should I plant it - the same level as in the pot where the graft is 6" above the soil OR should I plant below the graft?

I had the same type of tree and planted at the soil line in the pot and the next spring the grafted top part had died but the root stock came up instead. That's when I realized it was grafted and the bud union was exposed.