In message , Sacha
writes

Never tried, I'm afraid. We leave ours in but gardening here or in the
CIs is just so different. I'm not quite sure what the OP means by
bare root perennials, though. Bare root hedging plants, perhaps, such
a beech or hawthorn etc?

Come spring you can buy plants of some perennials as rootstocks -
hollyhocks, Gypsophila, paeonies, Liatris come to mind as examples of
the sort of plant sold that way.
--
Stewart Robert Hinsley