Leave them out, they die back completely over winter and be fine.

I agree with Mg,but I would give them a mulch for added protection,and maybe some grit on top..slugs especially, could lay their eggs in the soil..maybe add one or two slug pellets too,if you use them.

Cheers Bloom & Moon. The Delphiniums were a vibrant blue & it would be a shame not to keep them for next year. All other attemps in the borders have failed before

The new shoots are like a magnet to slugs and snails,Bill.I would leave them out next year,but just be one step ahead..Maybe a strip of copper band around your pot would be good.It stopped them getting to my Petunia's this year :o)

Copper pipe tee hee

A whole new meaning to 'Head Banging ':o)That would stop em in their tracks .Lol.