I usually plant mine in pots until they develop roots, then plant in the garden in the fall - some live, some don't. Even then, they seem very slow growing, even slowing growing than my seedlings.
This year, I have a group of very late prolifs from some late bloomers. So this year I have them in a pot, and after it gets cold and stays cold, I will try to bring them into my garage for the winter and see if this gives them a boost before planting them in the gardening the spring. My garage is insulated, and unless I leave the doors open, the temps stay reasonable - pop will get cold but not freeze if it is off the floor. I also have some south facing windows. I have successfully overwintered some flowers and some herbs in there, but the one time I tried to overwinter some late arriving day lilies from the auction ( expected them the next spring) I had major issues with aphids and rust. Hence the delay bringing this pot of prolifs inside, to try to prevent this.
But this is my first time trying this - I have no clue if I will be successful. I just keep experimenting....