Astilbe (False Spirea): a genus of 18 species of rhizomatous flowering plants, within the family Saxifragaceae, native to mountain ravines and woodland in Asia and North America. Some species are commonly known as false goat's beard, and false spirea. These hardy herbaceous perennials are cultivated by gardeners for their large, handsome, often fern-like foliage, and dense, feathery plumes of flowers. They are widely adapted to shade and water-logged conditions. They tolerate clay soils.