Canna lilies, often called cannas, are tropical plants prized for their bold foliage and vibrant flowers. While many gardeners propagate these specimens using rhizomes, starting cannas from seed offers a cost-effective and rewarding experience. Because the seeds possess a natural defense mechanism that prevents immediate growth, proper preparation is the first step in successful cultivation.
Preparing Canna Seeds for Sowing
Scarification
The first challenge in growing cannas from seed is penetrating the extremely hard outer shell. This tough coating must be manually compromised in a process called scarification to allow water to reach the embryo inside. Achieve this by gently nicking the seed with a small file or using sandpaper until the lighter interior is visible. Avoid damaging the inner embryo by filing away from the small eye-like spot on the seed.
Soaking
After scarification, the seeds must be soaked to hydrate the embryo. Place the nicked seeds in warm water for 24 to 48 hours. This soaking allows the exposed internal tissues to fully absorb moisture, beginning the metabolic functions necessary for growth. Observing some seeds swelling is a positive sign that water absorption is occurring.
Optimal Planting Depth and Medium
Planting Depth
Once the canna seeds are prepared, they are ready to be placed in a growing medium. The planting depth is shallow, ranging from one-quarter to one-half inch deep. This depth provides the best balance of moisture retention and access to oxygen. Planting too deeply prevents the shoot from reaching the surface, while planting too shallowly risks the seed drying out.
Growing Medium
The ideal growing medium is a sterile, fine-textured seed-starting mix that offers high drainage while holding sufficient moisture. A low-nutrient mix is preferred because the seed provides all the necessary energy for the initial sprout. Gently cover the seed with the mix, then lightly firm the surface to ensure good contact. Planting each seed in its own cell minimizes root disturbance later.
Creating the Ideal Germination Environment
Temperature Requirements
Successful canna germination depends on maintaining consistently high temperatures, reflecting their tropical origin. The soil temperature must be kept steadily within the range of 70 to 75°F (21 to 24°C) for the best results. This often requires using a specialized heat mat placed under the planting containers. Consistent warmth signals that the environment is favorable for growth, promoting the necessary enzymatic activity.
Moisture and Light
The growing medium needs to remain consistently moist, but it must never become waterlogged, which could lead to rot. Using a propagation dome or covering the containers with plastic wrap helps maintain high humidity. Initial light requirements are minimal, so containers can be kept in indirect light or darkness until the first shoots emerge. Germination may occur within a week or two, but it can take up to six weeks for all viable seeds to sprout.
Transitioning Seedlings to the Garden
Hardening Off
Once seedlings develop their first set of true leaves, they need time to adapt to outdoor conditions before final planting. This gradual acclimatization process, known as “hardening off,” is performed over seven to ten days. Start by moving the young plants to a sheltered outdoor location protected from direct sun and strong winds for a couple of hours around midday. Each day, progressively increase the time spent outside and the intensity of exposure to sunlight and wind. This slow transition toughens the plant’s cell structure, making it less susceptible to transplant shock.
Final Transplanting
Transplanting into the garden or large containers should only occur after all risk of frost has completely passed for your region. Ensure the outdoor soil temperature is reliably warm, ideally above 60°F. Cannas will struggle if planted into cold ground.