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.
A south European perennial, 2-3 ft. high, with whitish narrow leaves, and light-blue flowers in July and August. The variety alba or bicolor has white flowers marked with blue or rose at the base of the florets. It is easily raised from seeds and by division. C. lutea grows about 1 ft. high and has yellow flowers.