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 charming South European annual (also known as C. minor) grows about 1 ft. high, and produces its lovely funnel-shaped flowers from July to September in such colours as pink, rose, crimson, violet, white, striped, etc.
C. major (also known as Ipomoea purpurea), and popular as the "Morning Glory", has twining slender stems and beautiful funnel-shaped flowers of all shades of velvety colours - purple, scarlet, blue, white, etc, being represented.
Other species of Convolvulus grown in small quantities are C. Cneorum (or argenteus), a shrubby species 1-3 ft. high, with lance-shaped silvery-haired leaves and pale rosy flowers in summer; almost hardy. C. mauri-tanicus, a trailing North African perennial, with ovate roundish leaves and blue flowers with white centre, is often grown as a hanging plant for pots and baskets and for draping stones in rockeries. It may be raised from seeds, cuttings, and division.