This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The final stopping should be done when the plants are in the flowering pots, not later than the end of June. With quick-growing varieties the middle of July, however, will be late enough to stop the plants if an autumn and early-winter crop of flowers is desired. Varieties that make many shoots at the base of the plants, like Britannia, Mrs. Burnett, Mikado, etc, should be stopped not later than the beginning of June; others, like Enchantress, White Perfection, etc, can be stopped as late as the middle of July.
This should be attended to immediately after the final potting, and every shoot must receive attention, as each one now means a flower during the winter months.
The winter temperature should be kept as near as possible at 50° F. during the night, with a slight rise, say to 55° F., during the daytime. It is, however, advisable to commence firing rather early in the season in order to exclude the damp autumn air from the houses. After January the temperature may be increased by 2 to 4 degrees if the weather is fairly bright and congenial. Ventilation should be given daily if at all possible, even if the fires have to be forced a little more to keep the temperature at the proper point. Watering should be done sparingly during the winter; but in spring, when the plants are growing fast, plenty is required. About April, when the sun gets powerful, a daily syringing before noon will be found beneficial.
This must be attended to as soon as the buds are large enough to handle easily. This means, of course, that all except the crown or terminal bud on each shoot must be removed if long-stemmed flowers are required. Should pot plants be wanted for decorative purposes it is advisable to let all buds develop into flowers. Artificial manure should not be given until about Christmas, when a light dressing of bone meal will be found beneficial. Later in February, and especially from March and April onwards, when the plants grow very rapidly, some of the stronger and quicker-acting manures, such as guano and special carnation mixtures, that are now prepared by most manure merchants and Carnation specialists, should be given at frequent intervals. How much and how often depends upon the condition of the plants - if strong and fast growing a weekly dose would not be too much.