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.
There are several species all easily grown in ordinary garden soil, in open sunny spots. Amongst the best-known kinds are the following: alpinum l ft., blue; flavum, 1 ft, yellow; grandiflorum (fig. 219), 1-1½ ft., a splendid rose-red annual with many forms; narbonense, 2 ft., sky blue veined with violet; perenne, 1½ ft., bright blue with pink and white varieties; and usitatissimum, 1½ ft., the common flax of commerce, with blue flowers. These are all raised from seeds sown in the open or under glass in spring. L. arboreum is a shrubby plant, 1-1½ ft. high, with yellow flowers in summer.