Hi Neal, yes, the stem that came up was a pink single herbaceous peony. The tree that I planted was Hanakisoi, a double. I left it, it had a cute little bloom.
I forgot to mention, when I 1st started growing peonies, I planted TP Shojuraku (Chojuraku). The guys that did the winter clean up cut it to a nub
In addition, back then I didn't know the woody stem on a tree peony wasn't to be trimmed.
Needless to say, the idiot that I am was thrilled to see single pink blooms the following spring, thinking I had done such a great job growing this peony, LOL. It wasn't until years later, when I learned about the various types of peonies that I realized my error