Dig 'em up (if you planted one, you'll dig up ten); knock off as much dirt as possible, then let them dry for about a week; DO NOT wash them, you'll encourage rot; trim back roots and brush off remaining dirt; dust with a fungicide; put in a paper bag and store in a cool, dark place. You could throw in a couple of buckets of slightly damp peat moss if you like - I don't bother.

Another method I use: dig up, brush off soil, let dry a few days. Place roots (rhizomes) in a pail/bucket. Fill in around the bulbs and cover with sand. Store in (preferably) cool basement or crawl space.

Last year I got a beautiful scarlet flowered bronze leafed canna and was afraid I would kill it over the winter. I asked a neighbour what they did to overwinter theirs and they said they just dug them up, knocked off all the soil and let them dry for a few days. Then they just put them in a plastic (!) grocery bag and hung them on a nail in the basement.
I did that, but I left the one side of the handle hanging open so it would get some air and checked the bag every so often. It did fine and I potted it up at the end of March and it grew just fine this year.
I grew it in a large pot and it seems like it has multiplied quite a bit. I haven't watered it for a while and today I cut off the tops and am leaving the tubers in the soil. I am storing the pot in my basement. I will probaly dig up the tubers and separate them in the spring when I am ready to pot them up again.
I got three others this summer at an exchange and have also grown them in pots, so I plan to treat them the same.

Lois

If you have any extra dry peat moss, layer your dried corms in a large pail. Moisten the top layer every month just a little.
Store in your basement or warmest part of garage.
We usually have a large garbage pail each year. The unusual colours or varieties, I put in their own bag of dry peat and label well.

I thought we should wait till the first hard frost before digging them up? So does this mean we can dig up the cannas despite that they still are going strong? If so, I'll get to it this weekend.

While we are on the subject of cannas. I have managed to gather canna seeds. Does anyone know how to propagate these things?

Hi ianna, here is a link that can answer your question

Here is a link that might be useful: Canna Growing Tips