What Is the Canna Lily Hardiness Zone?

Canna lilies bring a tropical feel to gardens with their large leaves and showy flowers in vibrant shades of red, orange, yellow, and pink. While simple to cultivate during the growing season, their ability to return year after year depends on the garden’s winter climate. Understanding your climate zone is the first step in determining the proper care for these plants.

Canna Lily Hardiness Zones

A canna lily’s winter survival is determined by the USDA Plant Hardiness Zone Map, which organizes regions by their average lowest winter temperature. This map helps gardeners select plants that can endure local conditions. Canna lilies are reliably perennial in USDA zones 7 through 10.

In these warmer climates, the ground does not freeze deep enough to damage their underground storage structures, known as rhizomes. Gardeners within this range can leave cannas in the ground with minimal protection and expect them to regrow the following spring. Locations with zone ratings of 6 or colder experience winter temperatures too severe for the rhizomes to survive in the soil.

Growing Cannas in Hardy Zones

In zones 7 through 10, preparing canna lilies for winter begins after the first frost. Once the cold has blackened and killed the foliage, the plant has entered dormancy. At this point, the stalks should be cut down, leaving about 2 to 4 inches remaining above the ground. This helps to tidy the garden and ends the plant’s growing season.

After trimming the stalks, applying a thick layer of mulch is a good practice, especially in zone 7 or 8. A 4 to 6-inch layer of insulating material like shredded leaves, straw, or pine bark helps regulate soil temperature and protects the rhizomes from cold snaps. This ensures the rhizomes remain safe for spring.

Overwintering Cannas in Colder Zones

Gardeners in zones 6 and below must dig up canna rhizomes to save them for the next year. This process should be initiated after the first light frost but before a hard freeze can damage the rhizomes. A hard freeze, typically when temperatures drop below 28°F for several hours, can turn the water-filled rhizomes to mush, making them non-viable.

To lift the rhizomes, use a garden fork or spade to gently dig around the clump, staying about 6 to 8 inches from the plant’s base. Once the surrounding soil is loosened, work the tool underneath the root mass and pry the entire clump from the ground. Shake off large clumps of soil, but do not wash the rhizomes, as the remaining soil provides a protective coating.

The next step is to cure the rhizomes. Cut the stalks down to about 1 to 2 inches from the rhizome and move the clumps to a dry, sheltered location with good air circulation for a few days. This curing period allows cuts on the surface to dry, which helps prevent rot during storage.

For storage, place the cured rhizomes in a container with air exchange, like a cardboard box or a paper bag with ventilation holes. Pack them loosely in a medium such as peat moss or sawdust, ensuring each rhizome is surrounded and not touching another. The storage location should be a cool, dark area that stays above freezing, between 35°F and 50°F. A basement or unheated garage is a suitable spot to keep them dormant until spring.