Canna: Greenhouse Plants
C – cool, minimum of 7°C (45°F)
Tropical America and Asia
More closely associated with dot plants in municipal bedding displays there is no reason why these exotically flowered plants should not brighten up a greenhouse collection. The rhizomes, which need frost free conditions while dormant through the winter, should be started in February to give early flowers. Begin watering and give them a temperature of 15°C (60°F). If this is not possible then wait for temperatures to rise naturally and settle for later flowers. I prefer to let them come up in their old pots and then lift them out, divide and repot into a loam-basedas required.
Throughout the growing season they can be watered well and fed weekly until they begin to die down again in autumn. There are several species worth growing including a very showy variegated plant, Canna variegata, which has large yellow flowers. However, these are hard to come by. The most accessible are mainly hybrids of C indica which are available in red, pink, yellow and orange. The plants can be propagated by dividing or cutting the rhizome at planting time; also by seed. The seed is large and hard, so in order to speed up the intake of water that encourages germination it should either be soaked for 24 hours or the seed coat should be filed through. Germination is at its best in temperatures of 18-26°C (65-80°F). Plants should flower in their second year. Look out for C. irridiflora which is a large red-flowered species from Peru. This will grow well stood in the water of a greenhouse pond. There is no need for this plant to die down if warm temperatures can be maintained during winter.