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.
This distinct-looking composite forms a dense carpet of silvery-white foliage on the ground, and has white flower heads in June and July. It is easily increased by division, and is grown in fairly large quantities for sale. It flourishes in any good garden soil, but must have plenty of sun to develop the best colour.