They are supposed to be half hardy so will not survive our winters outside. Cut them back, put them in a large pot and cover with compost.Keep in a frost free shed or garage over the winter.

Thanks for that - would it be okay to over-winter them in the garage even if it gets no light? Unfortunately I don't have a green-house.

Yes you can bury your plant completely. I had mine in a black flower bin from the supermarket. I did put holes in it. I did not water it after it went away for the winter until I saw it start to grow away in the spring. They will come away earlier in a greenhouse but will be fine in the dark. Put them outside to get the light when they start to grow as long as it is not frosty.Put them inside again at night when there is any danger of frost.