Tender cannas do not survive frost or freezing temperatures. If your cannas are in pots, simply move them indoors before the first frost. They will live and bloom all winter in a warm room or greenhouse. If your cannas are in the ground, lift the rhizomes and store them indoors over the winter. Cannas can remain in the ground all year in frost-free areas.
Trim the aboveground portions of cannas just before the first frost, leaving 3- to 4-inch stubs of stem on the rhizomes. Alternatively, allow the first frost to kill the cannas. Then trim the black foliage and stems from the rhizomes, leaving 3- to 4-inch stubs.
Dig in a circle around each canna plant, loosening the soil by wiggling the spade. Circle an area wider than the original plant so you can lift new rhizomes along with the original. Dig 8 to 12 inches deep to loosen the roots.
Lift the canna. Remove it from the planting hole and brush away as much soil as possible.
Allow the rhizomes to dry for two to three days in a cool, protected place. Leave the dried stem stubs on the rhizomes. The bud for next year's plant is in the old stem section.
Place the rhizomes in mesh bags to hang, or on open shelves where air circulates freely.
Store cannas in a cool, dark place during the winter. Storage temperatures should remain below 50 degrees Fahrenheit. Examine the cannas once a month during storage to check for mold or fungus. Remove and destroy any affected cannas.