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.
The best species is Dyerianus, remarkable in a young state for the beautiful appearance of its large broadly lance-shaped leaves which are washed with a mixture of crimson, steel blue, and purple. It is easily raised from cuttings and during the summer months makes a fine bedding plant. S. isophyllus is an old favourite with pale-blue tubular flowers.