Taken from Eclectic Gardener @ www.teachinggarden.org
Written by Alan Hickman

So, in town we didn’t quite make it into November without a frost. Early Monday morning the airport recorded zero degrees a couple of times and a min-max thermometer, left in the back of my truck, registered minus two.In my rather sheltered garden at home, only the tender impatiens seemed much the worse for wear, but at the fairgrounds, a mile or so outside the built-up area where the temperature is usually five or six degrees cooler than at the airport, the devastation was complete. The massed plantings of dahlias and cannas were a sorry drooping mess of blackened foliage.
At last the tubers could be dug out and prepared for storage without destroying the best display that the plants had put on all season.
Each year since Peel Teaching Garden volunteers have been looking after the display beds at the fairgrounds, the number of tender tubers planted has increased exponentially. This spring several hundred tubers were planted and, with each plant producing five, six or more new tubers, methods have had to change in order to store the avalanche of riches.
The basic principles of course don’t change.
Before doing anything, if there is more than one variety of plant to be dug, make sure that each clump is properly labeled while it is still in the ground and its identity is remembered. There is nothing that looks more jarringly out of place than stray red cannas scattered through a bed of yellow ones.
While some tubers, like cannas, are pretty robust, others, like dahlias, are quite delicate, so it is as well to treat all the roots as if they were fine china. If you have built-up a good loam soil in the flower beds, then this year’s low soil moisture will make lifting the tubers relatively easy. Using a full-size spading fork - one with broad flat tines - loosen the soil around and under the root clump and gently lift out the tubers.
Fresh out of the ground, the skins of dahlia tubers are about as strong as wet newspaper so the less handling they get, the better. Put the clumps into a shallow tray, cut the foliage off with sharp secateurs, leaving an inch or two of stem, and let the clumps dry in the sun for a few hours. Although the skins of other tubers may be rather tougher, the flesh can still be bruised by rough handling before it has had a chance to dry and ‘cure’.
A day of autumn sunshine will get rid of the surface moisture and a couple of days in an airy frost-free garage should dry most tubers enough to allow for further preparation and perhaps sub-division. If there is only a dozen or so roots, they can be stored just as they are and they can be divided next year before planting. If storage space is limited, or if there is a lot of material, then the clumps can be split now and be stored as individual tubers. The trimmings and waste bits can be composted and the individual tubers will pack down into less space than the splayed-out clumps.
Canna clumps divide easily; just grasp the clump on each side and twist. Usually it will break in two at a weak point somewhere in the middle. The process is repeated until all the knobby bits with little spikes on the end are separated. Let the wounds dry and then the pieces can be packed with vermiculite in plastic grocery bags and stored in a cool but frost-free place over winter.Dividing dahlias is a rather more demanding task. Each tuber has a thin neck with a raised collar which is attached to this year’s flower stem. To be viable, each tuber must retain its collar and preferably also have a sliver of the stem. If the tuber’s neck is broken, if the skin is rubbed off, or if the collar is missing, the tuber will be ‘blind’ and it will not produce a new plant.
The keys to successful storage are low temperature and having low, but not too low, a moisture level. The temperature should be a lot closer to two than to twenty, but in most houses that is just not on. Often, the best that can be done is to store the packages on the floor, hard against an outside wall and as far as possible from a heat source, and to cover the bags with insulating blankets.
Vermiculite has the ability to retain and release moisture so, if the tubers start out at about the right dryness, they should remain stable in storage. For dahlias, if the skins are dry and are starting to shrivel just a bit, then they seem to have the best chance of survival.
As insurance, a couple of weeks after putting the tubers down, open one or two bags and check the contents. If all is well, re-pack and check again in a month and then a month later. If all is not well; unpack everything, discard any mildewed or rotting tubers, air dry what is left and re-pack in fresh vermiculite.
Large bags of vermiculite are available at Humber Nurseries, Hwy 50., Peel Seed Co-Op, Hwy 10 & Bovaird, and at other garden centres.