Cem what you have is the herbaceous rootstock that was used as the nurse root. Could be very nice or not. I had one that was a wonderful single white. The flower appeared to be made of wax. When I separated from the tree peony the white did not live.
The two spellings of the tree peony are both correct. Both are english translations of the spelling in Japanese and Chinese.
If there is enough tree peony cells remaining where the stem entered the nurseroot sometimes a tree peony will grow given time. Time can be up to 3 years or probably more. One of my at least took the 3 years and is a lovely plant after being eaten, stepped on and broken off .
