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 referred to as bulbs because the root structure closely resembles that of a classic plant bulb. In warm climates (USDA hardiness zones 8 to 10), canna bulbs can be left in the ground over winter, and the plants perform reliably as perennials, coming back year after year. However, north of zone 8, the bulbs will die if they spend winter in the ground. In colder climates, the plants are either treated as annuals and discarded at the end of the season, or the bulbs are dug up and stored for winter and replanted the following spring.
Storing the bulbs is fairly quick and easy, depending on how many you have to dig up. However, they require some monitoring while they're in storage.
Click Play to Learn How to Store Canna Bulbs for Winter
When to Dig Up and Store Canna Bulbs
Dig up canna bulbs for winter storage in the fall after 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 won't 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.
Before Getting Started
Over a growing season, a single canna bulb (actually a rhizome) can become much larger, developing offshoot structures. You can propagate new plants by cutting away these well-developed offshoots. This can be done in the spring, after you bring the store rhizomes out of storage, or when you dig them up in the fall. If you do it in the fall, it's a good idea to dust the cuts with sulfur powder before storing the bulbs, which will prevent fungi from entering through the cuts.
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 planted 4 to 6 inches deep, a shovel or garden fork will often be the best option. Keeping the shovel blade or garden fork 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 of the bulbs. 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 air-drying them in a warm, dry location for seven days. A well-ventilated garage or closet makes a good curing location. Curing toughens up the outer skins to help the bulbs resist rot during storage.
Wrap and Store the Bulbs
To store cannas indoors over winter, wrap individual bulbs in newspapers or small paper bags and include a small amount of dry, sterile growing medium, such as peat moss or vermiculite. The growing medium will absorb moisture and help to prevent rot. Place the wrapped bulbs in a cardboard box or large paper bag, and do not allow the bulbs to directly touch one another. Store 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.
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