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 Cucumber (Cucumis sativus) is an East Indian annual, having roughish, trailing, angular fleshy stems bearing large angular and heart-shaped coarsely toothed leaves, roughish to the touch like the stems, each one being borne alternately and opposite a succulent tendril. The yellow short-stalked flowers are borne in the axils of the leaves, but male and female flowers are quite separate and distinct from each other. The Cucumber is therefore monoecious, like its first cousins the Vegetable Marrow and the Melon. The female flowers are easily recognized by the swollen ovary at the base, which eventually develops into the well-known, oblong, cylindrical fruit. The development of this is not dependent upon fertilization, as in the Melon, and many growers therefore pick off all the male or staminate flowers, as they are only a hindrance to the formation of the fruit. If, however, it is desirable to obtain seeds, it is essential to retain the male flowers and transfer the pollen from them when ripe to the stigmas in the female blossoms, and thus secure fertilization. Indeed the production of good Cucumber seed is an industry in itself, and many growers devote almost their whole time to it.
The great aim, however, of Cucumber growers generally is to produce large supplies of fruit for the markets every year. Extensive ranges of glasshouses have been erected around the metropolis (at Enfield, Edmonton, Ponders End, Waltham Cross, etc.) and many large provincial towns expressly for Cucumber growing, and there are thousands of tons of fruit produced now where years ago there were only hundredweights. The span-roofed style of house is most favoured, and the length may be anything from 100 to 300 ft. long, while the width may be only 10 to 12 ft. An excellent and convenient size is about 200 ft. long by 13 ft. wide. Where, however, Cucumbers are grown as a "catch crop", as they often are during the summer months, any kind of glass structure with sufficient heating apparatus is utilized for the purpose.
Being practically a tropical plant, the Cucumber requires plenty of heat. Being also of a very fleshy succulent nature, and of quick growth, it must also have an abundance of moisture. But when the expressions "plenty of heat" and "abundance of moisture" are used in a horticultural sense they must not be literally understood to mean that there is to be no limit to either a high temperature on the one hand or to a supply of water on the other. Some growers in the past have, however, taken such expressions literally, and have grown their Cucumber plants in structures that could only be compared to a Turkish bath. The plants were steamed to death, with the result that their constitution broke down under the terrific strain, and the deadly "spot" played havoc with the crop. Such growers, instead of using their horticultural common sense, fled to the chemist (who knew little or nothing about the business) and wanted some concoction that would check, if not altogether kill, the disease. And the chemist, like a sensible man of business, immediately proceeded to compound his nostrums and to talk learnedly about the fungoid and other diseases of Cucumbers, at the same time not forgetting to take the fees to recompense him for his learning and skill.
Happily we have passed the stage where nurserymen used to "steam their Cucumbers up", and even houses were built without any means of ventilation so as to ensure the perfect "steaming up". Under such conditions, which were only too prevalent, it was not surprising that the goose that laid the golden eggs of the market nurseryman was nearly killed.