Canna's have delivered a brilliant display all summer, but they are not frost hardy.
Cut the stems back to 5cm above soil level. Lift the plants and shake off as muck of the soil as possible. Store in trays of sand with just the crown showing. Store in a frost free environment.
When emptying your pots that have your summer colour, don't waste the soil. Re-use it by mulching your borders or top dressing permanently potted plants. Mulching is an easy way to help improve soil structure, supress weeds and retain moisture.