This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
The cultivation of Tomatoes as described above may be carried out in glasshouses without any artificial heat whatever during the summer months. If crops, however, are desired during the winter and early spring months, it will be necessary to have the houses heated, and a night temperature of not less than 60° F. must be maintained. For early autumn crops the seeds should be sown in the way already described, about the end of May and during June. No artificial heat will be necessary, and the plants may be grown on strong and sturdily with plenty of fresh air and light surrounding them. For early-spring orops seeds should be sown in September, the young plants being transferred to 2 1/2-in. pots when large enough, and afterwards to 5-in. or 6-in. pots. In due course they should be placed in 10-in. or 12-in. pots, using a fairly gritty loam having a little leaf mould and basic slag mixed with it. By placing a slender bamboo stake to each plant the main stem can be tied from time to time as it grows, and all the laterals should be pinched out when they can be easily taken between finger and thumb.
As there is always more difficulty in setting the fruits of winter Tomatoes, care should be taken to keep the atmosphere pure and in a moving or buoyant condition on all days when the weather is mild and genial. If the stems are tied to wires or strings the latter may be strummed at intervals with the fingers at noonday for several days.
This will jerk the plants gently and cause the pollen when ripe to blow about and settle on the pin-like stigmas of the ovaries. A still safer and better plan is to tie a piece of fur or a rabbit's tail on the end of a stick and pass it over the flower trusses day after day when the sun is shining. This secures proper distribution of pollen, and eventual fertilization. It will more than pay for the time and trouble spent, by the fine crop of fruit later on. The illustration (tig. 497) shows a crop of "Winter Beauty" grown in pots in winter.
Fig. 497. - Tomato - "Winter Beauty". (Pot-grown plants).
To make sure of success, attention must be paid to keeping the temperature equable, about 60° at night and 65° to 70° F. by day. It will be almost fatal to allow the temperature to jump up and down with great fluctuations. Good stoking is therefore a necessity during the winter months.
The next point is to give water carefully, which means only when the soil is getting dry. The atmosphere should not be too moist, indeed it should be on the dry side; and if the plants are not placed too close together all the available sunlight will be utilized to the best advantage.