Astilbe's brightly colored, stately plumes comprised of tiny, densely packed flowers are absolutely spectacular when planted en masse and are one of the most colorful flowers for the shade. The panicles range in shape from tall and narrow to dense and stocky. Still others are more open and airy or cascade outward. In order to more accurately identify the traits of a particular cultivar, they have been divided into the groups listed below.
Culture: All types of astilbe require consistently moist soil that is rich in organic matter. Light shade or filtered sun is best. However, they will also grow in full shade but will not bloom as prolifically.
Simplicifolia Group: A species characterized by glossy, mid-green leaves which are lobed, not divided. Plants form compact mounds that look good even without flowers. Open, airy panicles of star-like flowers are followed by ornamental seed heads which provide a few additional months of interest. Slower to establish than the Arendsii Group, requiring about 3 years to reach maturity.
Arendsii Group: A group of hybrids developed by famed German nurseryman Georg Arends. Includes crosses of Astilbe chinensis var. davidii with Astilbe astilboides, and members of the Japonica and Thunbergii Groups. The resulting hybrids comprise over 95% of all Astilbe sold in the USA.
Astilbe chinensis: A later blooming species useful for extending the bloom season into late summer. Foliage is deeply incised, coarsely textured, and often bronze-green in color. Flowers are borne on narrow branched panicles. Though garden performance is far superior in moist soil, members of this species are moderately drought tolerant. Shorter varieties such as 'Pumila' make excellent ground covers.
Japonica Group:Noted for its early bloom time and glossy green leaves which are often tinged with red. Flowers are produced in dense, pyramidal clusters.
Thunbergii Group: A group of late blooming hybrids with distinctive open, nodding flower clusters held on tall stems above the glaucous foliage.