Common name: Indian shot plant
Cannas are best suited for greenhouses and conservatories in the UK.
The 75mm (3") long gladiolus-like flowers come in shades of orange, red or yellow, and this coupled with its banana like leaves makes for a very attractive plant at the back of the border*.
These sometimes green, brown or purple leaves can grow up to 600mm (24") long and 300mm (12") wide, and the plants can grow up to 1200mm (48") high.
*They can be placed out in sheltered borders for the summer months then returned to the greenhouse in winter.
Week 4-6: Soak seeds in warm water for 24 hours or cut a small nick on each seed to allow water to enter.
Sow singly in 3 in. pots* of compost and provide a minimum temperature of 21°C (70°F).
*Cell trays will do equally well.
Germination should take around a week.
When the pots / cells are nearly pot bound (filled with roots), pot on in the same manner as plants raised from rhizomes.
Week 16: Plant up the rhizomes in pots of potting compost, taking care to just to cover the growing tip.
Take great care with emerging shoots, they are extremely fragile.
Place the pots in a greenhouse / conservatory and maintain a minimum temperature of 16°C (61°F).
Plants for indoor display can be started into growth at any time.
The earlier a rhizome is started into growth, the sooner it will flower.
In mild areas rhizomes may start to grow of their own accord in a cool greenhouse in March.
Week 16: Pot up the growing plants into the next sized pot or into tubs and grow on at a temperature of 16°C (60°F).
Mature plants with more than one new shoot can be divided at this time.
Divide them into sections each with three growing points and pot into 200mm (8”) pots.
Again take great care with emerging shoots, as they are extremely fragile.
Week 23: When all risk of frost has passed move pots / tubs to a sunny, sheltered spot outdoors.
Alternatively, after all risk of frost has passed, set the plants out in a sunny, sheltered well dug and manured bed or border.
Canna are best planted in groups of three with each plant being 150-200mm mm (6"-8")) apart and the groups 500-600mm (18"-24") apart.
Plants benefit from mulching and should be watered and fed throughout summer, especially during dry spells.
Week 42-45: Lift and label rhizomes that have been planted out in garden once frost kills the foliage, and leave them to partially dry out, before cutting the leaves and roots off prior to winter storage.
Leave some compost attached to the rhizomes, and sprinkle with water occasionally to maintain humidity and keep in a frost-free place, at about 6°C/43°F.
Rhizomes shrivel and die when kept too dry, conversely when too wet, they rot.
Cannas are generally trouble free, but keep an eye open for virused plants.
Pests and diseases:
Spray plants in early spring as a precaution against aphids.
Slugs & Snails:
Place some slug bait around the base of young plants.
Slugs & snails have a penchant for tender young unfurling leaves rather than the coarser open leaves.
Red Spider Mite:
This pest can occasionally infest indoor canna.
The symptoms are dry looking leaves which turn uniformly brown.
If examined under a magnifying glass the underside of the leaves may show traces of a white powder (these are dried egg-cases) and profusion of tiny creatures running around.
Red Spider Mite is immune to most if not all the proprietary insecticides available to the amateur.
Spraying with a soap-based insecticides may dislodge and/or suffocate them, and minimise the problem to an acceptable level.