Cannas are sometimes called canna lilies, but they are not true lilies. Cannas are tropical plants that grow easily from tuberous roots called rhizomes. The rhizomes are tender, and are not frost or freeze hardy. They must be dug up in the fall and protected from cold temperatures over the winter, except in areas that do not experience freezing temperatures. As houseplants, most varieties of cannas will grow all year long.
Trim off the flower and foliage stalks on your cannas in autumn before the first frost. If a light frost has occurred and the stalks are black or withered, trim them immediately. Leave about one inch of stalk above the rhizomes when you trim them.
Dig the canna rhizomes. Your canna rhizomes have probably multiplied by producing new rhizomes, which are attached to the central mass. Dig a large enough area of soil to get all of the new canna rhizomes as well as the original.
Spread out the canna rhizomes in a cool place, and gently clean off excess soil. Trim dead leaves and plant debris.
Place your canna rhizomes in plastic bags in which you have punched a few holes. Use a little clean sawdust, sand or peat in the bags with the rhizomes. Store your cannas in a cool, but freeze-proof location.
A garage that does not freeze or a basement makes a good storage place for canna rhizomes. Do not keep them in a refrigerator, because temperatures will be too cold.