The lost 6 months - dry rhizomes

Revisit: The lost 6 months - dry rhizomes

Over-wintering Cannas

A rhizome is not a bulb. In botany, a rhizome is a horizontal stem of a plant that is usually found underground, and in Canna sending out roots and shoots from its nodes. Rhizomes may also be referred to as creeping rootstalks, or rootstocks. In general, rhizomes have short internodes; they send out roots from the bottom of the nodes and new upward-growing shoots from the top of the nodes.

For Cannas, the rhizome is used by gardeners to propagate the plants by a process known as vegetative reproduction.

So how does a rhizome differ from a bulb? A bulb is an underground vertical shoot that has modified leaves (or thickened leaf bases) that are used as food storage organs by a dormant plant. A Canna is never dormant, it is growing 52 weeks of the year. That is the bit that so many get wrong when handling their Cannas over the winter.

In the northern hemisphere, in England, our Cannas are growing outdoors for 6 months and spend the remaining 6 months being abused indoors! We see books and articles telling us to dry them out, cut of the roots and then leave them in boxes of peat until the spring. Watering is hardly ever mentioned. So all the Canna will be doing is draining its energy reserves stored in the rhizome to keep life growing. If it had a bad growing summer before it may not have enough food reserves to keep going and will just give up life. We have all seen rhizomes that do that.

So, what is the best way to over-winter a Canna. It certainly is not to leave it in a pot in a garage and ignore it for 6 months. While it may still have roots, it is in soil that the ever-hungry Canna will have depleted of minerals during the summer. Although it has roots, but no food, means it is drawing on energy in the rhizome during the winter months to keep going. The least that should be done in that case is to add fertilizer to the pot, lightly water and ensure that it never dries out. It will not produce any starch to plumpen up the rhizome when it has no foliage, but it will not deplete the rhizome of its stored energy.

There is an urban myth that says that if the first leaf in the spring is bad, then the Canna has virus. A little thought and understanding would reverse that, and the wisdom should be that a good first leaf indicates great health, but while early leaves may not be good, by the time the plant is growing with roots in well-treated soil if it is not producing better and better leaves, then it possibly has virus.

We often see what happens when you buy dry rhizomes from garden centres. They are usually withered and depleted of any stored energy. They are grown over the summer and people are disappointed. However, if given TLC during that first summer and over-wintered correctly then the plant will often amaze the next year, unless it has a bad infection of virus, which is a different matter altogether. So, I always recommend waiting until the second year before passing judgement.

So whatever method you use to store your Cannas over-winter, I would recommend that you ensure that it is kept ticking over for that long winter period.

The lost 6 months - dry rhizomes

Canna 'Uncle Sam', photo by Malcolm McFarland

For Cannas in the rhizome trade it is quite simple. They have the foliage chopped off and the rhizomes are ripped out of the field at first frosts, they go through a high pressure water spraying system that removes most of the soil still clinging to them. They dry for a week or so in a controlled temperature, then they are hand separated and packaged ready for sale.

Up until then everything went just fine for the Cannas, but now the problems start. The packaged rhizomes enter the distribution chain, and they spend their time in warehouses and despatch points in temperatures that are very often uncontrolled. Eventually, in January they arrive at the premises of the final part of the chain, the garden centres. There they go onto sales racks and any weak ones perish there, with no water, and little light. No more to say, except that they stay there slowly dehydrating until May and early June, when they get offered in 2-4-1 deals to cover up their disadvantaged state.

For the survivors, the rhizomes sold through the rhizome trade are normally very dry by the time they are sold to the public, and I feel that they should not be judged at all that first year. The rhizomes are normally very de-hydrated and the root system is normally dried out and useless. All the remaining energy stored in the rhizome has to be used to protect its very life existence and is mainly used to grow a new root system.

If it is planted in soil with little nutritious value, then it is now in a doomed cycle. Growing a new root system means it does not have the energy available to produce large, luxurious foliage or produce large expansive blooms. It will grow some foliage to allow the capture of more energy to keep it alive, and that will probably be sub-standard, showing its state of stress. It may produce minimum flowers in a desperate attempt to produce some seed to ensure its DNA lives on, but nothing that will enlighten the heart of a gardener. So the Canna manages to hang onto life, but the gardener thinks it is a poor variety and doesn't deserve to have space in the garden again.

Gardeners who give up on Cannas at this point have just lost out on one of life's raffles. So many, if nurtured properly through the winter and grown on in good conditions next year will more than make the grade. I believe that many plants thrown out as having virus are just heavily stressed through mistreatment. That doesn't mean that many don't have virus, I am sure that they do, but my guess is that at least 50% are just suffering from this mishandling during the lost 6 months.

Dry rhizomes for sale

The dry rhizomes are now in the shops, and this reminds me of an item in the Canna presentation that Keith and Christine Hayward deliver to gardening clubs, garden centres etc.

Keith always asserts that when you buy a packaged dry rhizome you always get three things:

1. a name
2. a picture
3. a rhizome

And the only thing that you can be sure of? None of them will match!

That certainly seems the case with the one on the left above. Canna 'La Gloire' is a medium sized Crozy Group cultivar; bronze foliage, oval shaped, branching habit; round stems, coloured purple; flowers are open, self-coloured apricot, staminodes are large, edges irregular, labellum is apricot, petals purple, fully self-cleaning; fertile both ways, not self-pollinating or true to type, capsules globose; rhizomes are thick, up to 3 cm in diameter, coloured purple; tillering is average. Introduced by Vilmorin-Andrieux, France, EU in 1920.

The one in the picture looks like a red, and it certainly is not apricot. So, it waits to be seen if the rhizome matches the above description, or is something totally different.

Cynically, I am tempted to add that you always get a fourth item - Canna virus!

Club secretary's or garden centres in the South of England wanting an interesting presentation should contact Keith and Christine at Hart Canna.