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 culture of the Lettuce has been practised in France for centuries, where, it is said, on account of the poorness of the meat, the taste for salads was developed among the people generally long before it had got beyond the most select coterie here. The art was brought over to England by French gardeners who established themselves in Bermondsey when that district was famous for its gardens, and at the present day the old French family names will be found among our foremost market gardeners. What is styled "French Gardening" is a system, practised chiefly in the neighbourhood of Paris, in which Lettuces are cultivated on manure heat under glass lights and cloches, in conjunction with other crops, which are cleverly worked in so that a constant succession is maintained through the greater part of the year. Frequently two or three crops may be seen coming along together. The system "pays" the French maraicher, who usually employs no labour except that of his wife and family, who knows neither half-holidays nor Bank holidays, who works on Sundays as long as on weekdays, who frequently takes his rest as he goes in his market cart to Les Holies (the markets), and who after all this is content to live with the strictest frugality.
Whether it "pays" in the generous English sense, which includes hired labour for the roughest of the work, and living in the degree of comfort our wiser economic conditions have happily made us familiar with, is another question.
The growing of early Lettuces under glass and the art of intensive cropping have been practised for generations by English market gardeners, only they have adapted their methods under the tuition of experience to our climate and our habits of business.
Lettuce plants for forcing on heat in the early spring are sown early in October in frames. When the seedlings are up they are all the better for being thinned, so as to give the others room and prevent "drawing". Those that are pulled out can be pricked into frames or covered with cloches. The time for planting out depends upon the form of heat used. Over hot water they can be planted in the beginning of January, and then a couple of crops can be got in before the main crop of Marrows or Cucumbers, or whatever is intended, is put into the frames. If the heat is obtained from manure it is well not to plant till February, because the manure will lose its heat quickly, if put down earlier, before the sunshiny days come. On manure heat the frames will need covering at night, but this is not necessary when hot water is used. Some people sow French Breakfast Radishes before planting the Lettuce. It is doubtful whether anything is gained by this. The Radishes are apt to crowd and hinder the Lettuces. Carrots also are sometimes sown before sowing the Radishes. This plan answers better on the manure heat than on the hot water, as the Carrots will hinder getting a more profitable crop in. The " Early Paris Forcing" Lettuce is the best sort for earliest sowing. Sutton's "Golden Ball" is a good sort for second season.
For Cos Lettuces, dark or light-green Paris will do. The Cos are more difficult to manage, because they are so apt to get leggy. Good Cabbage Lettuces will generally make 2s. per dozen, and the inferior grades 1s. to 9d. per dozen. The Cos, if well done, will sometimes make 2s. to 3s. per dozen at the very beginning, although the larger proportion will be sold at 1s. to 9d. per dozen.