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 bushy South European perennial, although nearly hardy, is usually grown as a cool greenhouse pot plant. It has ovate, deeply-toothed leaves, and masses of small violet - blue flowers. There is a white-flowered variety also. Plants are raised from cuttings or seeds, and thrive in sandy loam.