Grown from bulbs, cannas come in varieties ranging from dwarf to giant. What they all have in common, however, is that the bulbs produce flowers that are flashy and, compared to the size of the plant itself, huge. Cannas will only survive the winter outdoors in climate zones 9 and 10.
In any applicable climate zone, wait until frost kills the foliage of the cannas and then cut it off to just above the tops of the bulbs. Discard the dead foliage.
In climate zones 9 and 10, cover the cannas completely with a heavy layer of bark mulch, straw or hay.
In colder climate zones, dig the canna bulbs up.
Clean them of excess soil by brushing off the dirt gently with your fingertips, a paper towel or a soft clean cloth. Don't wash the soil off them.
Take the bulbs inside to a place where the temperature won't drop below 40 degrees Fahrenheit for the entire winter.
Separate the bulbs from one another with several inches between them and let them dry out for a few days.
Put the bulbs in a cool location for the winter. A heated garage or garden shed would be ideal, but what's most critical is that the temperature in the space where they're stored should stay between 40 and 50 degrees Fahrenheit.