Picture: Canna Lily growing beautifully in the landscape
Canna lilies (Canna spp.) are striking tropical and subtropical flowering plants native to Central and South America, with some species found in parts of Asia and Africa. They belong to the family Cannaceae and are the only genus within it. Though commonly called lilies, they are not true lilies at all. They have been cultivated for centuries — both as ornamental plants and as a food source, since their starchy rhizomes are edible — and today they are grown in gardens all over the world.
The most immediately striking feature of canna lilies is their sheer visual drama. Their large, paddle-shaped leaves come in rich shades of green, burgundy, bronze, purple, and even striped or variegated forms. Above this bold foliage rise tall flower stalks bearing clusters of vivid, iris-like blooms in red, orange, yellow, pink, and coral. Plants range from compact 60 cm dwarf varieties to towering specimens that can exceed 2 metres in height.
Cannas grow from thick, fleshy underground rhizomes that store energy and allow the plant to regenerate each season. In frost-free tropical climates they are reliably perennial, dying back slightly in cooler months before resprouting vigorously in spring. In temperate regions where frost occurs, the rhizomes must be lifted and stored indoors over winter, or the plants are simply treated as annuals and replaced each year.
These plants thrive in full sun and warm temperatures and are considered heavy feeders, responding enthusiastically to rich, well-amended soil and regular fertilisation. They tolerate consistently moist soil better than most garden plants and can even be grown at the margins of ponds. Given adequate sun, warmth, and nutrients, cannas grow rapidly and bloom prolifically from midsummer right through to the first autumn frost.
Canna lilies are ecologically valuable as well as beautiful. Their nectar-rich blooms attract hummingbirds, bees, and butterflies, while their dense foliage helps suppress weeds when plants are grown in groups. They have also been studied for their phytoremediation properties — their capacity to absorb heavy metals and pollutants from waterlogged soils — making them a practical choice for rain gardens and water feature edges.
In terms of garden design, cannas are exceptionally versatile. They serve as dramatic specimen plants, bold centrepieces in tropical-style borders, and eye-catching container plants on patios and terraces. Their combination of architectural foliage and vivid flowers makes them ideal as a tall backdrop for lower-growing plants, or as a living privacy screen when planted in a row. They pair beautifully with elephant ears, dahlias, bananas, and ornamental grasses to create lush, layered planting schemes.
Picture: Canna Lily Seeds
How to Grow Canna Lily from Seed
1. Growing cannas from seed is slower than planting rhizomes but is economical when large numbers of plants are needed, and it offers the exciting possibility of raising unique plants from open-pollinated seed.
2. Collect seeds from dried, brown seed pods on the plant in late summer or autumn, or purchase seeds from a reputable supplier. Choose plump, hard, dark brown to black seeds and discard any that are pale or shrivelled, as these are unlikely to be viable.
3. Scarify each seed before sowing by carefully filing or rubbing one side against sandpaper or a nail file until the pale inner layer just begins to show. Canna seeds have an extremely hard outer coat that prevents moisture from penetrating, and scarification is essential for reliable germination.
4. After scarifying, soak the seeds in a bowl of warm water for 24 to 48 hours. This softens the coat further and begins the hydration process that triggers germination. Seeds that sink to the bottom after soaking are the most likely to be viable.
5. Start seeds indoors 4 to 6 weeks before your last expected frost date. Fill small individual pots or deep seed cells with a moist, good-quality seed-starting or potting mix, and sow one seed per cell at a depth of approximately 2.5 cm (1 inch).
6. Provide consistent bottom warmth throughout germination. Canna seeds need soil temperatures between 21 and 27°C (70–80°F) to sprout reliably. A seedling heat mat placed under the tray is strongly recommended, particularly during the cooler months of late winter and early spring.
7. Expect germination within one to three weeks when seeds have been properly scarified and soaked and are kept warm and moist. Unscarified seeds may take several weeks longer or may fail to germinate at all, which is why the preparation steps are so important.
8. As soon as the first shoot emerges, remove the tray from the heat mat and move the seedlings immediately to a bright, well-lit position — a south-facing windowsill or under a grow light for 12 to 14 hours per day — to prevent weak, leggy growth.
9. Water carefully throughout the seedling stage. While cannas appreciate consistent moisture, waterlogged growing medium can cause root rot. Water thoroughly when the top layer of mix feels dry, and ensure all pots have adequate drainage holes with no standing water beneath them.
10. Begin fertilising with a balanced liquid fertiliser diluted to half strength, applied once every two weeks, once seedlings have developed two to three sets of true leaves. As plants mature, switch to a fertiliser slightly higher in potassium and phosphorus to encourage strong roots and flower development.
11. Pot up seedlings progressively as they grow. Cannas develop quickly and will outgrow small starter cells within a few weeks. Move them into increasingly larger containers to prevent them from becoming rootbound and to maintain the vigorous, uninterrupted growth that leads to earlier flowering.
12. About one to two weeks before transplanting outdoors, begin hardening off the seedlings. Place them in a sheltered, lightly shaded spot outside for a few hours each day, gradually increasing their exposure to direct sun, wind, and outdoor temperature fluctuations to reduce transplant shock.
13. Move seedlings to their final outdoor location only after all frost risk has passed and nighttime temperatures are reliably above 10°C (50°F). Choose a full-sun position with rich, well-draining soil, dig in plenty of compost beforehand, and space plants at least 45 to 60 cm apart.
14. After transplanting, water deeply and consistently for the first two weeks while plants establish. Once settled, maintain a regular feeding schedule throughout the growing season — every two to three weeks with a balanced or high-potassium fertiliser — to support the heavy feeding demands of these vigorous plants.
15. Be patient about flowering. Seed-grown cannas are slower to bloom than rhizome-grown plants and may not flower until mid to late summer in their first season, or in some cases not until their second year. Full sun and consistent feeding will help push them towards blooming as early as possible.
16. At the end of the growing season, once frost blackens the foliage, carefully lift the rhizomes that your seed-grown plants have now developed. Trim back the stems, allow the rhizomes to dry for several days, and store them over winter in a cool, frost-free location in barely moist compost or peat. Replanting these divisions the following spring will give you a much faster and more abundant display than starting from seed again.