This section is from the book "The Gardener V3", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
A few words on these points may perhaps prove to be words in season to many of our readers just now. For the present year the glory of the Dahlia has departed, for "November comes, with gloomy fogs begun, Through which, dim-looming, frowns his furrowed face: Like a huge globe of molten iron the sun Seems labouring through upon his daily race.
All nature speaks of changing and decay, "Which is not death, but sleep, to cease in spring's bright day".
These aspects of November bring with them cold days, and sharp white morning frosts, which soon have their effect on the beauty of the garden. Very shortly, therefore, the roots of Dahlias must be lifted and stored away for the winter.
It is somewhat singular that most writers on the cultivation of the Dahlia from some cause omit giving instructions how to keep the roots during winter. There are many different opinions current as to the best mode of doing this, and a variety of plans are carried out; but one that has borne the test of many years' experience is likely to have an interest for those anxious to be informed in regard to the matter.
Generally speaking, the roots of Dahlias are lifted in November. There is no great difficulty in keeping them through the winter. They should be got up on a dry day; but when taking them up, it is by no means necessary that all the soil should be shaken from the roots. A dry day is best, because the ground works better, and because the roots should be dried a little before storing them away for the winter. Some of the old school of florists, and probably some of a more modern date, used to wash their roots very carefully indeed from all soil adhering to them, and then dry them as some do Potatoes for exhibition purposes nowadays. Careful as they were, all their attention could not prevent the roots from decaying sometimes. Some growers made a point of keeping them in dry sand, packed in boxes: this was the plan recommended by James Hogg of Paddington, the renowned Pink cultivator. Some placed them in pits as they would Potatoes, and covered them with straw and mould. Others would strew them about an underground apartment. Some have been known to sew them up in a Russian mat and hang them up in the coal-cellar. Others would put them into dry mould and stow them away underneath the potting bench.
One enthusiastic amateur grower used to hang his roots round the walls of his kitchen, in the hope of thus escaping all chances of disappointment; rot they could not, at least from damp, and freeze they could not, for the kitchen fire prevented that. Another, no doubt quite as enthusiastic in the matter, recommended that, "for the tender small bulbs which will not bear drying too much, that they be potted on taking them up from the ground, and have a slight watering to close the mould about the roots, and then kept in the dry till wanted." Generally, among amateur growers, this dry place was the kitchen or sitting-room. It was contended that "the roots, in short, require to be only kept from heat, frost, and wet;" and to those who had hitherto failed to preserve their roots during winter, the following piece of advice was tendered: "To let the roots dry the same as they would a bulb or a pod of seed before they are stored, for if put away damp there is great danger of the rot".
Now for a more modern, but in our own experience as well, thoroughly successful, mode of wintering the roots of the Dahlia: "Select a dry day for getting them up, cut the tops clean off to within an inch of the crown with a small saw, lay the roots on some sticks or flattened boughs, so placed in the ground that the air can pass through them, with the neck downwards, and with as much soil in the tubers as will remain after they have been poked with a small stick, which is the best tool to remove the soil with. If the weather is fine and dry, the roots may be removed to their winter quarters in three days, care having been taken that they have been covered with mats at night, and the covering taken off each morning. The floor of a greenhouse I consider the most suitable place in which to keep them during the winter; or, if the grower does not possess a greenhouse, a dry cellar will answer the purpose, or any room where frost will not penetrate. A little ventilation is always necessary to prevent mould.
When valuable roots, such as seedlings or other scarce kinds, are required to be kept in plump condition for early forcing, I would recommend that they be taken up from the ground with all the soil that can be lifted with them, and that they be at once placed in large pots in a dry place".
The writer of these valuable directions (Mr C. J. Perry of Castle Bromwich) also alludes in a somewhat amusing style to an error sometimes committed by growers - "that of drying the roots too much. Many a time," he says, "have I seen them suspended in some coachhouse or loft, until nearly all the juices have been dried out of them. They were then consigned to a warm room, where no frost could penetrate, and by the time they were required for propagating, half the tubers were as dry as old sticks".
A great deal depends on properly drying the roots previous to stowing them away: they should never be dried up so as to present a shrivelled appearance, but merely the surface of the tubers dried, and the stems cut off as recommended. None of the greener portion of the stem should be left, as it would certainly decay during winter, and endanger the crown, which is the portion of the root most necessary to be preserved. Those who have a greenhouse can keep the roots well under the stage, which is a good place for the purpose, excepting only that they usually give a slovenly appearance to the house, which ought always to be a picture of neatness.