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.
This is usually started the second or third week in September. If possible, all houses should have sulphur burnt in them before the Chrysanthemums go in, and should be thoroughly dry. Overcrowding should be avoided, as weak-necked blooms are the result of this shortsighted policy. All the air possible is now required, but no heat should be turned on before the blooms begin to open, and not even then unless damping becomes apparent. Attempts should be made always to get the house dry in the daytime, watering as early as possible; if the air is heavy, a little heat turned on early in the day is advisable to get the air on the move.
The ventilators should be open on mild nights; on damp ones the houses should be closed to keep the dry air in, unless of course the outside temperature is too high to permit it. Feeding, as advised before, should be done as required, discontinuing it when the flowers begin to open. If any variety begins to grow soft, two doses of superphosphate, ¼ oz. to a 10-in. pot, at three-week intervals will stiffen it up. It is possible to make a soft stem as brittle as an icicle by this means; bone superphosphate should be used in preference to mineral, and should be mixed with 3 parts of soil.
As before stated, every endeavour should be made to keep the selection of varieties up to date, a keen lookout being kept for good novelties, and all inferior sorts being promptly discarded. The growth of each variety needs studying, and a universal treatment avoided. The finer-rooted varieties require smaller pots, and must never be over pot ted. It will be found that the smaller-leaved sorts do best when only allowed to carry one stem to a plant from the first stop, while the heavier varieties may carry two or even three with advantage. The October and November varieties usually require two stops, and the December ones one stop and a natural break. It is wise to try all new varieties with stops at different dates to find the right treatment for the locality. Singles are grown in the same way as the doubles, and the disbudded large-bloomed varieties require quite as much care. The sprays require three stops, the last from July 1 to 15, and the disbudded ones two. Only stiff-petalled varieties should be grown with at least two rows of florets. Outdoor sorts usually require to be struck rather later, and after being hardened off in a cold pit can be bedded out in another one in good soil, planting at a distance of 6 in. by 4 in. After danger of frost is over, they require lifting with a fork and carefully planting in permanent quarters; well-hardened plants will stand 3 or 4 degrees of frost. All ground for outdoor varieties should be deeply dug, well manured, and dressed with lime during the winter, and, if at all poor a week before planting, dressed with 1 cwt. of sulphate of ammonia to the acre.
A natural break suits most outdoor varieties; or find out when the first natural break of each sort occurs, and stop the next at that date, or even a trifle earlier.
Eighteen inches each way is the best distance for planting, four rows going to each bed, and 2-ft.-6-in. paths being allowed between them.
A careful record should be kept of each variety, and a suggested form is given below.