Because of its large leaves Canna dislikes windy conditions since this can tear the leaves to shreds, so find a sheltered place for your plants in the garden. For best growing conditions it requires a deep rich well-drained soil and a sunny position.
Canna is not a hardy plant, although it can survive temperatures down to about -5 Celsius degrees (23 F) over-winter, it needs a good mulch if left in the ground in mild areas. In frost-prone areas the tubers must be over-wintered in a cool but frost-free place, in a conservatory or greenhouse, covered in moist soil or leaves. Harvest the tubers in late autumn, after the top growth has been killed back by frost and store them over the winter.
Slugs may be a problem for the Canna, as they love the young growth in spring and can cause serious damage to plants. Try to protect the plants form slugs to make sure they will not kill your plants.
Propagation of Canna can be done by seeds or root cuttings. The seeds are small, globular, black pellets, hard and heavy enough to sink in water. They resemble shotgun pellets giving rise to the plant’s common name of Indian shot. Allow seedheads to dry on plants then remove them and collect the seeds.
If you choose to propagate your plants by seeds, pre-soak them for 24 hours in warm water and sow them in late winter to early spring, in a warm greenhouse or indoors at 20 Celsius degrees (68 F). Sow seeds 2-5 cm deep in individual pots. Scarifying the seeds can speed germination, especially if the seeds have not swollen after being soaked. The seeds usually germinate in 3-9 weeks. Grow the plants on in a greenhouse for at least their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts.
If you want to propagate Canna by root cuttings, divide root clump as the plant comes into growth in the spring. Each portion must have at least one growing point. Pot up the divisions and grow them on in the greenhouse until they are well established and then plant them out in the summer in their permanent position.
Avoid planting out young plants until all risk of frost has passed as the frost may damage the new growths. Water regularly during the growing season, avoiding to let them dry out between waterings and apply a phosphorus-rich liquid fertilizer each month for optimum results.