sorry, don't know what does work, but since no one else has chimed in, I just want to let you know that leaving it in the water does *not* work.

Do not ask me how I know this.

I just do.

I bought a canna from ebay. She told me that it was taken from a Pond. She said that it would do fine on a soil and pot. It got stressed for a week or two and now it's doing find.

So what's my point here. I'm assuming that the storing/overwintering techniques used for potted cannas or cannas planted in ground should be the same.