Tree paeonies are hardy - to a certain extent. We have them in the garden for 20+ years and they are quite happy to -10C. Two winters ago we had -15C and thought that it had killed one of them but, after cutting back the dead wood it came back as good as new.

Hi Barbara and welcome to GoY, where do you live in the UK, is your soil neutral to acidic and how have you planted the tree peony?

Hi Moon growe,
Have my peony in medium plant pot in normal compost from Garden centre. Looked at roots and they seem to be rotting accept for one little tiny, tin white root coming as tho' it's fighting back ha! I am taking back to garden centre for credit and may be buy another next year - don't know...B

When you bought it from the Garden Centre you needed to either repot into a much larger pot or into the ground.