Following on from the Musa basjoo FAQ, here’s another – Cannas
05 July 2014 - by Lizzy Browne

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.

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