How do I over-winter cannas indoors?
Cut the plants back to within 4 to 6 inches of the ground a few days after a hard, killing frost. Then carefully dig up the canna clumps with a spade or garden fork. Leave a small amount of soil around the cannas. Allow them to dry for several hours. Afterwards, place the cannas in large boxes, wire crates, or in mesh bags. Store the cannas in a cool (40 to 50 degree Fahrenheit), dry location.