Back to some reality and some things that are actually happening here. I bought some canna rhizomes in spring 2013 and a couple of growing plants. Unfortunately the rhizomes, like so much canna stock, was full of virus. Canna virus has spread like a …. virus in recent years and it can be difficult to find ‘clean’ stock. Look out for distorted leaves, streaks of pale colour in the leaves or flowers, poor growth with lack of height and vigour and variegated flowers where they should not be. If you have signs of virus you must destroy the plants or it will spread to all your stock. So my rhizomes from Parkers, which were all affected, were dumped but my two, unnamed plants were healthy and I have kept and split the plants so from my two potfuls I had eight last year and now more than 30. And that was without really trying.
Although cannas are pretty hardy if you leave them in the ground overwinter here, if they do survive they come into growth so late in spring they hardly get into their stride before autumn stops them in their tracks. So it is best to lift them. Now they can be dried off completely and kept dry, of soil and leaves, to be restarted in spring but again, that does not give them a flying start in spring so I like to keep them just ‘ticking over’ in winter. You do not need much heat and 5c is enough. So I lifted the clumps in November and they were allowed to almost dry out. I would usually pot them but various reasons meant I could not and they were occasionally watered but the leaves were kept dry to avoid rot. I then, slightly earlier than I would like, split the clumps and potted them. I do not use a knife for two reasons: it is better to pull the rhizomes apart so they break where the rhizome this thin so the would is as small as possible and because a knife can spread virus if you do have stock that is infected.
I then cut off or snap off all the stems that have flowered. These will naturally die anyway once they have bloomed. I then cut off or pull off any dead leaves and they are potted into the smallest possible pot – not always very small when you have to fit the often long rhizomes in the pots. I do not water immediately but let the compost get quite dry before I water so the wounds can heal and not rot. Because I do not need hundreds of plants but will use them as ‘dot’ plants to create bold clumps in the garden I have put a good clump of rhizomes in the pots. For the next month or two they will get moderate watering to allow them to search out for water in the pots and then, as temperatures and light increase, they will get more water and liquid fertiliser.