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.
Some modern market gardeners who have large unheated glasshouses utilize them during the winter and spring months for the production of early Radishes. One of the largest growers in this way is the firm of Messrs. Smith, of Feltham and Isleworth, Middlesex. In the latter district twenty-one large glasshouses, covering about 10 1/2 ac. of ground, are put down in Radishes after a crop of Tomatoes. From 36 to 40 lb. of seed is necessary to sow 1 ac. of ground, and about 20,000 to 30,000 bunches of Radishes constitute the crop to the acre. The seed is generally sown about January and February, and Radishes are fit io pull by the second or third week in March, and continue till the end of April or early in May, when the ground is wanted for the summer Tomato crop. Radishes grown in this way realize about 1s. or 1s. 3d. per dozen bunches. [J. W].