The canna lily is an herbaceous perennial, which grows from a rhizome--a structure that looks similar to a bulb. In cold climates, these tender rhizomes need to be dug up and properly stored during the winter season. In spring, the rhizome clumps can be divided to be used in other areas of your garden or they can be planted as a full clump.
The canna lily has flat, broad green, variegated (green with white, cream, pink or red), brown, maroon or bronze leaves depending upon the cultivar. Flowers grow up through the base of the leaves or false stem--they are iris-like in appearance, and come in a variety of colors including red, orange, yellow, or a combination of these colors. The majority of canna lilies are 4 feet tall or less, but range from 2 ½ feet to 10 feet. Cannas thrive in organically rich, well-drained soil. They will tolerate most soil conditions if the site is well drained and the plants are fertilized. They can be planted in full sun or shade.
Canna is not a True Bulb
Cannas are not true bulbs. According to the University of Illinois Extension, “a bulb is any plant that stores its complete life cycle in an underground storage structure.” A complete life cycle consists of a basal plate from which roots grow; primary storage tissue; a skin like covering to protect the primary storage tissue; shoot/developing flower and leaf buds; and lateral buds. The canna does not store its complete life cycle in its rhizome/storage structure. Its rhizome is a structure that stores nutrients. The rhizome grows horizontally underneath the soil.
Canna Rhizome Basics
Rhizomes are tender storage structures and can easily be killed by cold winters. When grown in areas with cold winters, you'll need to remove the canna rhizomes from the soil after the first frost or when the foliage has dried up at the end of the growing season.
After the first frost, prune back the tops of the plant, leaving 3 to 4 inches of the stem. Use a garden fork or spade to dig them up--dig a few inches away from the base of the canna plant so you do not damage the root structure. Allow the soil to dry and then gently remove the soil. Apply a fungicide, and then store them in a cool, dry place. The temperature should not go above 50 degrees F. Place them on a shelf or hang them in a mesh bag--air should be able to circulate around the clumps. Clumps can be divided in the spring before planting or left as full clumps.
Dividing Canna Rhizomes
Dividing the rhizomes is not difficult. Divide in spring when you are ready to plant or replant the rhizome clumps. Unlike other tender bulbs, canna rhizomes do not have any buds or growth points on the rhizome itself. The new growth buds are within the old stem base of the canna, which is at the top of the rhizome clump. Therefore, when you are dividing the canna rhizomes, make sure that you include part of the old stem base with each part of the root that you divide--if you do not include part of the old stem base, the rhizome will not grow. Use a knife to cut apart the rhizomes, including part of the old stem base/new buds. The canna's tuberous root is then ready to plant. Plant them approximately 4 to 6 inches deep and space them 1 to 2 feet apart. Apply a 5-10-5 or 5-10-10 fertilizer after planting.