"Chris Hogg" wrote
IME you can move them almost any time, but we live in a very mild part
of the country and it may be different where you are. I also find that
any bits of root that get left behind will tend to send up shoots and
a new plant re-grows in the old position. I have a Mrs. Popple that
I've dug up several times but still it comes again!

I've found the same thing with hardy fuschias. Once established their
roots seem to go down really deeply.

I once had a largish F. magellanica that just upped and died for no
apparent reason. I cut the dead top down and hoped it would regrow from
the bottom but after several months nothing had happened so it was dug
out. The following year when I was about to plant something different in
its place, small shoots of a new fuschia had sprung up from some small
piece of remaining root.

--
Sue