American sites have it as hardy to -12C, so I'd plant it deeply in the ground and mulch it. Potted it needs a huge pot and sulks after a few years.
The picture of it
potted on the commercial sites shows a good plant in a tub, rather than a pot, and I doubt it would do as well for the next year.
Also available from Suttons, but their page has funny code and won't link!
Thanks for the nudge to let me know the named form is available.
I'm buying three for a big clump that will be cut down each winter.
I'm not
alone in preferring it as a clump of foliage.
Chad
ps. Charlie, the spell checker isn't present since the upgrade.