This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Next to the Wallflower or Sweet William the Foxglove is still worthy of attention by the commercial gardener, and those who specialize in root crops more particularly. The plant must be regarded and treated as a biennial, as indeed it is; hence the seeds should be sown in the spring of each year and flowered the following summer. The plant is of the easiest cultivation, growing freely in any good garden soil, and not opposed to those of chalk or sand. In cool and shady places also it thrives quite well.
Sow the seeds in the open in March or April, the former for preference, covering the seeds very lightly. Transplant the seedlings during showery weather when large enough to handle. Early transplanting should be practised, as upon the making of a large rosette of leaves in the season of planting a good flowering afterwards depends. Late sown or late vegetating seeds may not flower the year following the sowing, hence the desirability of starting early. Put out the seedlings into their permanent quarters when large enough. There is a considerable range of colour through white, cream, primrose, rose, and red; the strains known as "giant" and "gloxinia" flowered being the best. [e. h. j].