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.
This hardy North American shrub, with obovate leaves and clusters of twisted fringe-like yellow flowers, is the best known. Other kinds are arborea, japonica and its variety Zuccariniana, and "mollis - all from Japan and China. All kinds flower on the leafless branches between December and March. They grow in ordinary soil, and are raised from layers.