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.
These constitute an easily grown and lucrative crop either when grown in frames during the winter months or in the open air in spring, summer, and autumn. For early frame culture the Turnip-shaped or Round Red varieties are favoured, the "Forcing Scarlet" being one of the best. The first sowing may be made in September, on warm sheltered beds sloping towards the south, to produce a crop about the end of November or early December. If the weather is unfavourable, it may be necessary to cover at night with mats or litter.
In November and December Radishes are also sown in frames in which Carrots have already been sown and in which Lettuces are to be planted, and as range after range is cleared of the crops, so Radishes may be sown again beneath or between the Lettuces and over the Carrots until February and March. At the end of January and onwards, Radishes are also sown in the open borders, but the same system of over and under-cropping is carried on. The growth naturally is slower than under the frames and cloches, but the crops are successive and continuous throughout the summer and autumn months. Owing to the abundance of water and the beautiful mould, Radishes as grown in French gardens are tender and delicate in flavour, and are never allowed to become overgrown, spongy, and rank in flavour. Besides the Early Forcing varieties, others like the French Breakfast, the Half Long Scarlet, white - tipped, and others may be grown. The first early crops or primeurs, done up in bunches of a dozen, often realize 1d. and 2d. per bunch (1s. to 2s. per dozen bunches), each containing twelve Radishes. Open-air bunches, however, have from three dozen to four dozen Radishes in them for the same money later on.