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.
This quick - growing European annual is usually grown with Cress (see p. 190), although another plant, Rape (Brassica Napus), owing to its somewhat milder flavour, is often substituted for it. The roundish white seeds of Mustard germinate quickly, and for salad purposes the stalks are cut quite young before the true leaves begin to appear, and are packed in punnets in the same way as Cress. A fresh crop can be obtained every week or so during the season by means of repeated sowings.