I have a tree peony that I bought 3 years ago. When I planted it there was no indication of a grafting problem. However, the following year as the tree sprouted, so did the roots and up came what appeared to be a regular peony. Last year this didn't really bother me because it was sort of a 2-for-1 situation, first the tree bloomed (3-4 flowers) and then the regular peony bloomed. This year though, the tree still only had 3 blooms but the regular peony really went to town and unfortunately it didn't bloom very nicely.

I'd like to get rid of the regular peony and keep the tree, is this possible? Is there a way to dig this up and separate the tree from the regular peony and then seal the area so that the regular peony doesn't return?