Someone else asked this - and the answer was to trim the leaves off when they're coming to an end, and put the pot in a frost-free place. That's what I shall do!

I do as Christopher Lloyd, my gardening hero and a great Canna man - leave them alone until the first frosts have blackened and shrivelled the foliage (don't cut it down before!) then cut to ground. You can then in mild areas just mulch over with a good 2in layer of stuff, or, of harsher local climate, lift them and store in a tray of lightly moist compost in a dark cool place till putting out again in spring.

My cannas were fine left outdoors for 6 years (in Brighton) until just last year when the unusually hard winter carried them off.

thankyou for your suggestions!

I shouldn't worry too much at the moment. I grow water cannas and these are all still in the process of flowering in the pond. Being truly aquatic they can stay wet all the time without rotting as long as the roots don't freeze they will be fine. If you take a look at my page on here you can see all of them in the pond and also catch up with my blog as to the winter home they have being built for them as we speak. This will be ready for the end of this month as I know some forecast organisation says snow for the south east last week of October. My canas won't be exiting the pond until the first frost is forecast. I'm not going to let them get blackened by it as I am going to keep them ticking over all winter by heating their accomodation if necessary.