Somewhere I read that they form the buds which become shoots.
In winter. But I imagine it depends on how cold winter is for them.
I would like to see a temperature chart for what peonies do over the winter.
I don't want to dig a bunch up to see for myself.
But maybe one year I could plant one in some kind of translucent container, and bury it in fall
under mulch. Then I could dig it up and re bury the container over the winter.
