Planning winter storage

We have now arrived at the time of the year when we have to start planning what to do with our Cannas over the winter. Last Saturday saw the temperature drop to 8Deg Centigrade, which is low enough to start slowing down the excellent growth that Cannas should be making during September, when they come to a crescendo of flowers and new foliage.

Those with only a few Cannas to look after can decide to bring indoors into a conservatory and keep them growing over the winter, as Canna is a 52 week plant, or to wait until the frosts and move the plants indoors into a garage or shed after cutting down the foliage.

Our approach is to dig the plants out of the beds in which they are growing, using a garden fork to minimise damage, and to retain about a third of the plant, which is then planted in soil inside one of our three poly tunnels. This involves a lot of work, but will provide much new compost from the foliage and stalks.

Canna is a plant from the tropics and sub-tropics, and just being under the ground and inside a tunnel is not enough protection from the winter weather, as last year we recorded temperature of -10F in the main tunnel, so we will also cover the plants with horticultural fleece. Those with small unheated greenhouses may be able to do the same.

Others prefer to remove all soil, wash and allow to dry for a few days and then store in damp newpaper, vermiculite or perlite in dry conditions about 8F. 

The first shoots of spring?

It may look inconsequential to most people, but the photo above shows the first Canna shoot of the year for us at Claines Canna. The plants are all in the soil inside poly tunnels, where they have been since the frosts cut down the summers top growth last October.

The weather has now turned and the first signs of spring can be seen; of course we still have a way to go before we can say that winter is truly over, but the winter blues have now left the writer and we can look forward to better things ahead.

One of the advantages in using a polytunnel is that the specially formulated plastic covering traps heat from the sun and the daytime temperatures in the tunnel will be at least double those shown on the graph above. This has the effect of heating the soil during the day and when the outside temperatures drop overnight that stored heat will double the tunnels' overnight temperatures, as shown above.

If a Canna enthusiast has just a few specimens then the time honoured advice to store in a greenhouse or garage is still the most appropriate, but for anyone with a large number of plants to over-winter I would suggest that they consider growing in the ground inside a poly tunnel as a serious, proven, and practical approach.

Missed the solstice!

The winter solstice occurs at the instant when the Sun's position in the sky is at its greatest angular distance on the other side of the equatorial plane from the observer. Depending on the shift of the calendar, the event of the winter solstice occurs some time between December 20 and December 23 each year in the northern hemisphere, and between June 20 and June 23 in the southern hemisphere, during either the shortest day or the longest night of the year.

Anyway, I took my eye away for a moment and I missed the solstice. Those who read this blog regularly will know that I am always keen to know when the shortest day has arrived, so that I can start looking forward to Spring and Summer once again. It's all mental mind-play to save the winter blues taking over.

Although I missed it, it has definitely arrived and our days will now start getting longer! Yippee!

I have today finished moving all the cleaned and cut for-sale rhizomes into "flat" trays filled with peat compost, and moved them all into a shed with frost protection. This also makes me feel contented that the worst of the winter work is over and now we can relax a little until the time arrives in about two weeks time to start planting seeds!

Unfortunately, last winter we had two electricity cuts, which destroyed that year's crop! This year we have installed paraffin heaters to provide the main heating, supplemented by the fan heaters with frost controls. There are 105 trays for sale this year, but some only have a handful of rhizomes available, whilst the more vigorous, like Canna 'Musifolia Grande', have hundreds of rhizomes for resale.

Worst summer ever - official

This summer appears to have been the wettest since rainfall records began in 1914, according to provisional data from the UK's Met Office.

Britain had 358.5mm of rain, just beating the 1956 record of 358.4mm.

The main reason for the high rainfall has been the unusually southerly position of the jet stream, a band of strong winds high in the atmosphere.

Following earlier floods in central and southern England, five areas of the country are still on flood alert.

The record rainfall was driven by conditions in England, where the downpour surpassed all other recorded years by a substantial margin.

Summer of disappointment

"These figures confirm what most people have already been thinking - this summer has been very wet and very disappointing for most," said the Met Office's head of forecasting.

While it has been wet, the summer has been distinctly average in terms of temperature. June, July and August saw a mean temperature of 14.1C, almost exactly the average for summers since the 1970s.

The jet stream, a ribbon of very strong winds about 10km up in the atmosphere which brings weather systems to the UK, has been much further south and stronger than usual this summer. This has brought depressions across many parts of the country.

How are Cannas surviving?

So, way out of their natural area, how are Canna surviving in this turbulent, dysfunctional climate? Surprisingly well, as it happens.

Not only did our Cannas suffer too much water, and no oxygen at root level with the swamped soil, but they also had very little light. Cannas rely on light to power their leaves, the world's best starch producing engines, into producing starch that will be accumulated down at root level to produce the famous Canna rhizomes. Without light the engines merely ticked over occasionally when the conditions allowed.

Many other plants have just given up on 2006, however Cannas have stuck in there and now there has been a few weeks of sunshine and warm temperatures they are producing good quality foliage and bursting into flower, albeit a month late! Of course, it is heartbreaking to see Cannas only half the size that they should be, but the majority have now reached a decent size, albeit very few are their normal size. All the mature Cannas have flowered now, which is also pleasing.

However, the Cannas that have suffered most are this years seedlings. I would estimate that no more than 2-3% have flowered yet. Many are in the process of producing flower spikes, but will not open for several weeks. Others are still growing foliage and will not flower this first year. That means that very few can be disposed of this Autumn as not being special enough to grow-on, which in turn means major storage problems over the winter, as we have over 400 seedlings growing this year.

Anyway, we are just grateful for what we have and we will have to use our ingenuity to overcome the winter storage problems. So what has the photograph at the top got to do with the summer weather? Nothing really, other than this is an old cultivar that we collected this year from a collector in Italy, and we really like the photograph!

Summer splits

An article in this months R.H.S. "The Garden" caused me to review what I had done over the last few years and wonder if splitting Cannas can be done better. Although dividing perennials is usually a job for spring or autumn, recent findings suggest that, for some plants, summer division is better.

Firstly, although we treat Cannas as perennials, in reality they do not need rest and in their native environment they grow for 52 weeks of the year, only slowing down if temperatures go too high. In temperate climates we know that they will be destroyed by freezing temperatures and so we store them in a safe environment over the winter and early spring, until the threat of frosts is past. The risk of too high temperatures is not a problem.

Cannas do not have a true state of dormancy, they simply have an ability to survive bad weather and growing conditions in the wild, things such as fires and drought. The large store of starch in the rhizomes means they have the energy to start over again. Anyway, after subjecting them to intense distress over the winter months, we then split them and start them into growth. In the process we always have a high number of casualties, not surprising when you think that they have been in a state of extreme stress for six months, then we aggravate that by splitting them and expect them all to grow a new root system as well as top growth for us to admire.

The garden trade knows that if they don't sell the rhizomes in the spring, then they won't sell many later. So, it makes sense that the trade cleans, splits and packages over the winter for a spring sale. The trade normally sells them in packs of three, so the customer has a high chance of getting something to grow, even if the rhizomes have been subject to bad storage and display conditions.

For gardeners with an established collection of rhizomes, it may be better to plant the established, semi-dormant clumps back in the ground and then, when they are flourishing again, with a proper root system, to split them. What make me start thinking about this? For the last few years I have been trading plants with another enthusiast in July/August, and I have been splitting the rhizomes for exchange the week before his arrival. Within weeks, my own plants have recovered and thrown lots of new, fresh growth and my gardening friend has lost none of his newly potted plants.

It is noticeable that the splitting has added new zest to the plants, but it is probably just the fresh food in the new potting compost or the bone meal that I add first before replanting in the ground, and the handful of fertiliser afterwards which creates that effect, and makes them appear to outperform their companions.

Anyway, I have determined to give it a try next year, and instead of working in the cold and damp of the winter in a poly tunnel, I will leave our collection alone and just replant them in May, and then do the splitting during the summer, when I can enjoy the exercise and weather. For those not convinced, why not try splitting just one of your plants this summer and try it for yourself?