Canna lilies are tall flowers with tropical colors and dramatic foliage,. Better yet, they keep growing and spreading so you get more of these plants. You'll need to separate them and you can then spread the bulbs out in the same area or plant them in new areas for more color and interest.
Dig up the canna lily bulbs after the foliage has turned yellow. Digging the bulbs up before this will prevent them from collecting and storing nutrients for next year's growth.
Use a shovel to mark a circle around the plant, then carefully dig under and lift up chunks of soil holding the canna bulbs. Be careful not to let the shovel blade cut the bulbs. You may need to dig up a fairly large circle, larger than the diameter of the plant, in order to retrieve the bulbs intact.
Wash the clumps of bulbs by soaking them for a few minutes in a pot of water, hosing them off gently, or pouring water over them with a watering can. Gently shake off clumps of dirt. Washing the bulbs allows you to see better to separate them.
Separate the bulbs from each other with your hands. Wear gardening gloves if you don't want to get dirty. Gently pull the bulbs away from each other. Use small pruning shears to clip away roots of other plants or weeds that may be binding the rhizomes together.
Store the bulbs in a cool place until you're ready to plant them. If you plant to store the bulbs for a long period of time, it's best to store them in clumps, unwashed, and do the washing and separating just before you plant, according to Ron Cornwell, an educator with the University of Illinois Extension.