Are Canna Lilies Annuals or Perennials?

Canna lilies, with their broad, tropical leaves and vibrant flowers, are a striking presence in summer gardens. Their dramatic foliage, which can be green, bronze, or variegated, adds texture and height long before the showy flowers appear. A frequent point of confusion for gardeners is how to classify these plants.

The Annual vs Perennial Classification

The classification of canna lilies hinges on climate, which is why they are known as “tender perennials.” This term means that while the plant has a life cycle longer than one year, its ability to survive the winter is dependent on the local temperature. In their native tropical and subtropical regions, they grow as herbaceous perennials. For gardeners elsewhere, their survival is determined by how cold the ground gets during winter.

The United States Department of Agriculture (USDA) Plant Hardiness Zone map is the standard guide for this. Canna lilies are reliably perennial in zones 8 through 10, where they can be left in the ground year-round. Gardeners in Zone 7 can also leave them in the ground, but this requires extra protective measures to insulate them from the cold. In zones 6 and colder, the ground freezes deep enough to damage the plant’s rhizomes, so they are treated as annuals and will not return without intervention.

Growing Canna Lilies as Perennials

For those gardening in USDA zones 8 and warmer, canna lilies can be managed as low-maintenance perennials that remain in the garden. The foliage should be left standing until the first frost causes it to yellow and wither. This period allows the plant to continue photosynthesis, sending energy down to its underground rhizomes for storage.

After the first frost has blackened the leaves, the stalks should be cut back, leaving about 2 to 4 inches above the soil line. This helps mark the plant’s location and removes the decaying foliage, which can help prevent disease.

In the cooler end of their perennial range, such as Zone 7, an additional step provides valuable insurance against an unusually cold winter. After cutting back the foliage, apply a thick layer of insulating mulch over the plant’s crown. A 4 to 6-inch layer of organic material like shredded leaves, straw, or pine bark helps shield the soil from deep freezes. This protective blanket helps ensure the rhizomes below ground do not sustain damage.

Treating Canna Lilies as Annuals

In colder climates, typically USDA Zone 6 or below, gardeners who wish to save their cannas must dig them up for the winter. This process begins after the first light frost has killed the foliage but before the ground freezes solid. The frost signals the plant to enter dormancy, making it the ideal time for removal. Use a garden fork or spade to carefully lift the entire clump of rhizomes from the soil, taking care to dig wide around the plant to avoid piercing them.

Once lifted, gently shake off the excess soil and move the clumps to a dry, sheltered location, such as a garage or covered porch, for a few days to cure. Do not wash the rhizomes, as the remaining soil can help protect them from drying out too much in storage. During this curing period, the outer surfaces of the rhizomes will dry slightly, which helps prevent rot during their long winter storage.

For storage, place the cured rhizomes in a container like a cardboard box or a crate. They should be nestled in a storage medium that prevents them from drying out completely without holding excess moisture. Materials like peat moss, vermiculite, or sawdust are effective options. Store the container in a cool, dark, and dry location where temperatures remain consistently above freezing but below 50°F (10°C), such as an unheated basement or insulated garage. Periodically check the rhizomes throughout the winter and discard any that show signs of rot or have shriveled completely.