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.
Where large unheated greenhouses exist, some growers utilize them during the winter season for a crop of Cabbage. The seeds are sown in August, and the plants are ready to be put in during October and November, so as to be off by the middle or end of March. About 1 1/2 lb. of seed is required to produce enough plants (40,000) for an acre of ground, the plants being placed about 1 ft. apart every way. During the winter, however, every alternate one, if large enough, is pulled and sold as "greens", thus leaving about 2 ft. of space between the Cabbages that are to heart up later on. A good variety to grow under glass in this way is Hursts "First and Best", nice heads of which will often realize 1s. 6d. per dozen. It is not such a good variety for the open air, as it sometimes rots at the base of the head, and this is not noticed till cutting takes place. [J. W].