This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Dwarf or trailing North American shrubs useful for carpeting the ground with their evergreen foliage. G. procumbens grows 4 to 6 in. high, its white tubular flowers appearing over the lance-shaped leaves about July and August. G. Shallon, 2-3 ft. high, has broadly heart-shaped leaves and racemes of pink and white flowers. There are a couple of Himalayan species (nummularioides and trichophylla) and one from New Zealand, antipoda, not well known. They like a peaty soil, and are increased by seeds, layers, or cuttings.