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.
As soon as the plants have done flowering, plunge them in some suitable material in a sheltered position, where they have the advantage of the sun at least half the day, and secure perfect drainage by standing the pots on pieces of slate. Cinder ashes will be found to be a good plunging material. Stake all straggling growths, so as to secure them from injury, and supply water moderately, but constantly, as required; pinch out flower-buds as they appear, and be watchful for mildew and green-fly, preventing the spread of the former by first syringing the plants with water overhead, and then dusting them with sulphur; and getting rid of the latter by syringing, and then applying Pooley's tobacco-powder.
Should the plants be allowed to remain here until the winter sets in, additional covering at the roots will be required to protect them from frost. Some dry litter, or sawdust, or coal-ashes can be placed over the pots to the depth of about 3 inches; but it is much to be preferred that the plants have the shelter of glass before hard weather sets in. At this period water will scarcely be required; and when it is applied, it should only be in sufficient quantities to keep the wood from shrinking.
Plants destined for winter-blooming should be pruned, then potted, and the wood dressed with the mixture prescribed above. If the roots be dry, a soaking of water should be given, and the plants placed in a cold frame, or some other cool structure, where the buds will begin to swell; and by the end of the year they can be put into a warm house to be pushed on into growth, or treated as prescribed in my former paper. A. Kerr.