Canna is one of several beautiful tropical garden plant species that can be successfully grown in northern climates if special techniques are used. 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 in these climates, the plants perform reliably as perennials. However, north of zone 7, the bulbs will die if left in the ground over winter, so the plants are either treated as annuals, discarded at the end of the season, or they are dug up and stored for winter and replanted the following spring.
Cannas are expensive bulbs, so there is a strong incentive to dig and store these bulbs before winter falls. The same techniques used to dig and store cannas can also be used to save other tropical or sub-tropical plants that return annually via bulbs, tubers, or rhizomes, such as elephant ears or caladiums.
Why Canna Bulbs Need to Be Dug up and Stored
Like most tropical plants, cannas are "cold-tender" plants that 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. If these tropical species are subjected to freezing temperatures, water in the cells freezes and expands, rupturing the plant tissues. Thus, these tender plants need to be protected from freezing temperatures in order to survive over the winter in colder zones.
Storing and Replanting
Dig up canna bulbs for storage in the fall once the foliage has died back but before deep frost has arrived. Most gardeners do so 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 once a deep frost has penetrated the ground, the bulbs will be ruined.
Replant the bulbs in spring after the ground has fully thawed and all danger of frost has passed. This means late spring for most gardeners.
- Working time: 15 minutes for each bulb
- Total time: Several days of curing is required before bulbs are stored
- Material cost: A small bag of peat moss costs about $15
What You'll Need
- Trowel, shovel, or garden fork
- Newspapers or paper bags
- Peat moss or vermiculite
Every experienced gardener insists that their method of storing canna bulbs is the very best, but this method is widely accepted by many plant experts.
Dig up the Bulbs
Just about any digging tool can be used to dig up canna bulbs, but the relatively deep planting depth (4 to 6 inches) means that using a shovel or garden fork will be the best option. Keep the shovel blade well away from the plant stalks, then dig down and lever the bulbs up 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 the foliage back to 2 to 3 inches of the top of the 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. This curing helps to toughen up the skins of the bulbs, which will help them resist rot.
Store the Bulbs
To store cannas over the winter, wrap the 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 any moisture and prevent it from rotting the bulbs. Keep the bulbs in a cool, dry location that does not fall below 40 degrees F.
Periodically inspect the bulbs over the winter. If you find spots of rot on any of the bulbs, either discard the entire bulb or trim away the rotted portion.
The following spring, carefully inspect all the bulbs and discard any that are soft or rotten, then replant the rest.
Tips for Storing Bulbs
- Cannas that have been planted in pots can be stored right in the containers without digging them out. Cut the foliage down to soil level, then move the entire container to a cool, dry location that will not fall below 40 degrees F; a basement or the inner wall of an attached garage can be an ideal location.
- This same digging and storing technique will work for many tropical plants that grow from bulbs, corms, or rhizomes, such as elephant ears (Alocasia spp.), blood lily (Haemanthus multiflorus), caladiums (Caladium bicolor), 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 saved bulbs survive the winter.