Canna ~2013~

I'd be inclined to cut off the main stem, then let the cut dry.
Then store in barely damp peat or even some compost at low temperatures but above freezing.
The rhizome is small and will lose a lot of water if kept bone dry, equally the main stem will remove water if allowed to stay.
Just my guess.

Its the kind of division that is best found in spring when it can be potted up ready to grow away.

 

Thanks pete I'll cut off the stem now on the smaller rhizome pieces and let them dry . I store all my rhizomes in slightly damp compost . My big ( now huge ! ) Canna rhizomes I'll divide when potting up in March.