Advice
Canna cultivation
Cannas
are tender perennials that have experienced a revival in gardens.
Their cultivation requirements are quite simple.
Starting off
In early April encourage rhizomes into growth in a frost-free glasshouse (minimum temperature 10ºC/50ºF). Divide congested clumps of existing stock at this time into sections with two or three growing points. Plant into a 15-20cm (6-8in) diameter pot, using any good potting compost, so that the crown is just below the compost surface.
Growing on
Water sparingly until shoot and root growth is well established. Then increase watering and apply a well-balanced liquid feed periodically. Good light is essential so that plants produce strong, sturdy growth. Ideally maintain a temperature of 16ºC (61ºF), although plants will tolerate cooler conditions.
Planting out and aftercare
Avoid planting out until late May, when all risk of frost has passed. The planting site should be open and sunny and the soil should be enriched with organic matter and a general purpose fertiliser. Space cannas 60-90cm (2-3ft) apart, depending on the vigour of the cultivars, and water in well. Keep well watered and feed with a balanced liquid feed throughout the growing season.
Overwintering
Cannas are lifted after the foliage has been blackened by frost. Remove dead leaves and loose soil and store in trays of sand, coir or vermiculite, with the crown just showing. Keep just moist in a cold, frost-free greenhouse or conservatory. Container-grown plants can be stored in their pots.
Plants can be risked outdoors in well-drained soils in the mildest regions by protecting the crown with a thick layer of dry winter mulch such as bark
Further information
Conservation and Environment Leaflet - Energy Conservation in Greenhouses