Canna lilies (Canna x generalis) are striking tropical and subtropical plants prized for their large, paddle-shaped leaves and bright, showy flowers. These herbaceous perennials grow from modified underground stems called rhizomes, which multiply rapidly beneath the soil. Propagating these plants is a straightforward process for multiplying your stock, revitalizing overgrown clumps, and ensuring the continued health of your garden display. Propagation can be achieved through two primary methods: dividing mature rhizomes or starting new plants from seed.
Preparing for Propagation
The optimal time for propagation is during the plant’s dormant period, ideally in late winter or early spring before new growth emerges. Dividing the rhizomes while the plant is actively growing can cause stress and reduce the chance of successful establishment. If your cannas are planted in the ground, carefully lift the entire clump by digging about a foot away from the main stems to avoid damaging the rhizome mass.
Once the clump is lifted, gently shake or wash away excess soil to expose the rhizome structure. Preparing a clean workspace and sterilizing your tools is important to prevent the spread of soil-borne diseases. A sharp, sterile knife or clean bypass pruners are needed to make precise cuts during division. Having a fine powder, such as a garden fungicide or household cinnamon, ready will help seal the cut surfaces against rot.
Dividing the Rhizomes
Rhizome division is the fastest and most reliable method for producing genetically identical copies of the parent plant. The goal is to separate the mass into smaller sections, each containing at least two or three “eyes.” These eyes are the small growth buds from which new stems will sprout. Examine the cleaned rhizome clump to locate these eyes and identify natural constrictions where divisions can be made.
Use your sterilized cutting tool to make clean, deliberate cuts, ensuring each resulting section is firm and plump. Discard any old, soft, or shriveled sections of the rhizome that lack visible growth eyes, as they are unlikely to sprout successfully. After separation, the newly exposed cuts must be treated to prevent fungal infection and rot before they are replanted.
Dusting the cut surfaces generously with a powdered fungicide or ground cinnamon creates a protective barrier against pathogens. The divided rhizomes should then be placed in a dry, shaded area and allowed to “cure” for 24 to 48 hours. This curing process forms a protective callus over the wound, significantly reducing the risk of water absorption and subsequent rot when planted.
Starting New Plants from Seed
While rhizome division guarantees a clone, propagation from seed offers a chance to create new and unique varieties, though the resulting plant may not be true to the parent type. Canna seeds have an extremely hard outer shell, which must be compromised through scarification to allow water to penetrate and trigger germination. Achieve this by lightly filing or nicking the seed coat with a metal file or nail clipper until the pale, inner tissue is visible.
After scarification, soak the seeds in warm water for 24 to 48 hours to soften the seed coat and fully hydrate the embryo. Plant the prepared seeds in a seed-starting mix, pushing them about a quarter-inch deep and ensuring the soil is kept consistently moist. Canna seeds require a warm environment, ideally between 70°F and 75°F (21°C and 24°C), often necessitating a heated germination mat.
Initial Care for Newly Propagated Canna Lilies
Warmth is a prerequisite for successful establishment, whether planting divided rhizomes or newly sprouted seedlings. Divided rhizomes should not be planted outdoors until the soil temperature is consistently 60°F (15°C) or warmer. Planting in cold, wet soil can cause them to rot before they sprout. When planting the cured divisions, place them horizontally a few inches deep with the eyes pointing upward, then water thoroughly once.
For newly planted rhizomes, withhold further watering until green shoots emerge, which can take up to three weeks. Seedlings started indoors should be transplanted once they have developed two or three true leaves and all danger of frost has passed. Before moving indoor-started material into full sun, they must be gradually acclimated, or “hardened off.” This involves placing them in a sheltered area with partial shade for a week. This transition prevents sun scald and shock, allowing the plants to develop the vigor needed to thrive in their permanent, sunny location.