Canna is one of several tropical garden plants that can be grown in northern climates with specialized care. Technically, the roots of cannas are rhizomes, but they are commonly known as bulbs because the root structure closely resembles that of a classic bulb. In warmer climates (USDA hardiness zones 7 to 10), canna bulbs can be left in the ground over winter, and the plants perform reliably as perennials. However, north of zone 7, the bulbs will die if they spend winter in the ground. So the plants are either treated as annuals and discarded at the end of the season, or they are dug up and stored for winter and replanted the following spring.
Why Canna Bulbs Need to Be Dug Up and Stored
Like most tropical plants, cannas will perish if subjected to freezing temperatures. While cold-hardy plants have a mechanism that allows their cell tissues to drain water as temperatures fall, cannas and other tender plants lack this mechanism. So cold temperatures can cause the water in their cells to freeze and expand, rupturing the plant tissues. Thus, these tender plants need to be protected to survive over the winter in colder zones.
When to Store and Replant Canna Bulbs
Dig up canna bulbs for winter storage in the fall once the foliage has died back but before deep frost has arrived. Most gardeners dig up their bulbs immediately after the foliage has been killed by the first light frosts in fall or early winter. Light surface frost will not penetrate down to the buried bulbs, but a deep frost can ruin them.
Replant the bulbs in spring after the ground has fully thawed and all danger of frost has passed. This usually means late spring for most gardeners.
Equipment / Tools
- Trowel, shovel, or garden fork
- Newspapers or paper bags
- Peat moss or vermiculite
Dig Up the Bulbs
Just about any digging tool can be used to dig up canna bulbs. But because the bulbs are typically around 4 to 6 inches deep, a shovel or garden fork will often be the best option. Keeping the shovel blade away from the plant stalks, dig down and raise the bulbs out of the soil. Use your hands to loosely separate the bulbs and attached stalks from the surrounding soil.
Remove the Foliage and Clean the Bulbs
Next, cut back the foliage to 2 to 3 inches from the top of each bulb. Gently wash the loose soil off the bulbs. But do not thoroughly scrub them, as this can scratch the bulbs and make them susceptible to rot.
Cure the Bulbs
Before storing canna bulbs, it is best to cure them by placing them in a dry location for a few days. A garage or closet makes a good place to cure the bulbs. Curing toughens up the skins, which will help the bulbs resist rot.
Store for Winter
To store cannas over the winter, wrap individual bulbs in newspapers or paper bags with a small amount of dry growing medium, such as peat moss or vermiculite. Do not allow the bulbs to directly touch one another. The peat moss will absorb moisture and help prevent rot. Keep the bulbs in a cool, dry location that does not fall below 40 degrees Fahrenheit.
Monitor the Bulbs
Periodically inspect the bulbs over winter. If you find spots of rot on any of them, either discard the entire bulb or trim away the rotten portion. The following spring, carefully inspect all the bulbs, discarding any that are soft or rotten. Then, replant the rest.
Tips for Storing Canna Bulbs
Cannas that have been planted in pots can be stored right in their containers without digging them up. To store them like this, cut the foliage down to soil level. Then, move the entire container to a cool, dry location that will not fall below 40 degrees Fahrenheit. A basement or the inner wall of an attached garage can be an ideal location.
Furthermore, the digging and storing technique for cannas will work for many tropical plants that grow from bulbs, corms, or rhizomes. These include elephant ears, blood lilies, caladiums, and dahlias.
Don't be discouraged if you lose a few bulbs to rot or severe desiccation. Experienced gardeners are generally happy if 80 percent of their bulbs survive the winter.
Pearce, R. Plant Freezing and Damage. Annals of Botany, vol. 87, no. 4, 2001, pp. 417–424., doi:10.1006/anbo.2000.1352