Q. What are Cannas?
A. Cannas are rhizomatous perennials, i.e. they have a horizontal, underground storage organ (rhizome) that produces the downward root system and upward growing shoots. Their common name, Indian Shot, refers to the hard, pea-size seeds, resembling shot gun pellets. They’re essential plants for the exotic, lush, jungly garden and produce exotic flowers over a long period. Some of the smaller species cannas even associate well with cottage garden plants. They also make bold plants for patio containers. In addition to the green leaved varieties, some have dark bronze, burgundy foliage, others have incredible variegation. Flowers come in a huge range of colours including creamy/white, pink, red, orange and yellow. Some flowers are multi-coloured. Large varieties, producing giant, almost banana-tree-like plants rarely produce flowers in the UK.
Q. Are they hardy?
A. Some Cannas are hardier than others and will survive average UK winters, but many unfortunate gardeners had their whole collections wiped out by the severe winter of 2009/10, so assume not.
Q. How big and how fast will they grow?
A. They range in size from about 1m to 4m. Growth is rapid from mid summer and most cannas multiply quickly. A plant in a 2L pot can be divided into 2 or 3 plants the following year.
Q. Will they grow in pots?
A. Almost any plant can be grown successfully in a pot and provided it is supplied with adequate food and water and re-potted when required, they make fantastic pot plants. However, size may be restricted in a pot.
Q. What’s the best position and soil type for Cannas?
A. Cannas love the sun but will tolerate part shade, though they will be less floriferous. They appreciate a deep, rich, moist soil.
Q. How much food and water should I give them?
A. Plenty. Lots of feed during the growing season and lavish them with water. This is the key to successful Canna cultivation. Well-grown plants, bursting with health, are not only more attractive but are more resistant to disease such as Canna virus. Many cannas can be grown as pond marginals.
Q. What do I do with them in the winter?
A. After the first frosts have blackened the leaves, lift the cannas, shaking off any loose soil and place in the smallest pot the rhizome will comfortably fit into. Fill gaps with peat based compost. Don’t place in a large pot. Lots of compost around the rhizome/roots may lead to rot. Move the pot to a frost-free environment such as shed, garage, greenhouse, spare room. If there is a possibility that building may not be frost free in exceptionally severe weather, wrap the whole pot in several layers of horticultural fleece, hessian etc. Do the same with pot grown specimens. Now the trick is with the watering. They shouldn’t spend the winter in dust but must not be soaked. Keep barely moist. If you’re lucky enough to own a heated conservatory, take inside before the foliage is ruined by the frost and enjoy your evergreen plant through the winter months.
Q. Isn’t that a lot of trouble to go to?
A. No. It sounds more trouble than it actually is. And look at it this way; a hanging basket takes much longer to assemble than planting a Canna, it costs more, and most people are prepared to sacrifice basket plants to the frosts. Clearing away a basket full of dead plants takes about as long as lifting and potting a Canna for winter storage. When you consider that these magnificent Cannas have beautiful, tropical foliage, and flower for the same length of time as a hanging basket (not to mention possessing more impact and distinction), its really no trouble at all to make sure the plants survive so you can enjoy them again the following summer.
Q. I’ve been told that I should clean the stems and all the soil and roots from the rhizome so I’m storing the rhizome only. Is that correct?
A. In our experience, not only is this a lot more work, but also, the failure rate is higher than the method we now employ.
Q. How do I divide my Cannas?
A. Divisions should be taken in spring, as the new shoots begin to emerge. Tip the Canna out of its pot and cut away roots and soil. Using a sterile knife cut the rhizome into pieces ensuring each has a growing bud. Dust cut surfaces with Flowers of Sulphate powder (available from garden centres, hardware stores) to prevent rot. So now from one pot of Canna you have several pieces of rhizome. Place these in the smallest pot or seed tray you can and cover with compost. Keep barely moist. In warm weather root and shoot development will be rapid and the plants can be re-potted. Gradually increase watering.
Q. My Cannas have started to produce shoots - when can I plant them outside?
A. Cannas shouldn’t be planted outdoors until all risk of frost has past – usually the beginning of June in England. In the preceding weeks, harden off plants by placing outside during the day and leave outside at night if mild, just as you would with bedding plants. Plants that are subjected to severe cold will have their growth checked.
Q. Why have my cannas got puckered, streaked leaves and are flowering prematurely?
A. These are the classic signs of Canna virus. Cannas showing these symptoms will fail to thrive. Do not buy Canna rhizomes. Buy plants from a reputable nursery. Before buying plants inspect the leaves carefully. Ask the nursery staff about the virus and where their stock comes from. Avoid Dutch or Chinese plants. If you take home virused plants, they will infect your clean stock. If you suspect any of your cannas have virus be ruthless and dispose of them before the disease spreads. When dividing your plants dip the tools in a solution of bleach to prevent the spread of the virus. Avoid buying cannas from car boot sales.
Q. I’ve been growing Cannas for several years and now have dozens. Should I sell them at a car boot sale?
A. Please see above question.
