Astilbes are sometimes called false spirea, false goat's beard or meadowsweet. Native to Asia and North America, they are hardy perennials that grow well in U.S. Department of Agriculture plant hardiness zones 3 through 9. The flowers are feathery plumes that range from white to magenta, and the ferny foliage is glossy and medium to dark green, sometimes with a bronze tinge. Astilbes tolerate shade but will produce more flowers with exposure to dappled light or cool morning light. They need moist soil. While there are several species of astilbe, most plants found in nurseries and garden centers fall within four major groups.
Astilbe Arendsii Group
The hybrid Astilbe x arendsii group is named for George Arends, a German perennial breeder. In fact, it's estimated that approximately 95 percent of astilbes sold are from this group. Heights range from 2 to 4 feet. Many variety names hint at their German origins, such as "Brautschleier" or "Bridal Veil," "Amerika" or "America," "Glut" or "Glow," and "Erika" or "Erica." "Brautschleier" bears white flowers, "Amerika" bears violet-rose plumes, "Glut" has deep maroon flowers, and "Erika" produces pink blooms while its foliage has bronze overtones.
Astilbe Crispa Group
The hybrid Astilbe x crispa group doesn't have as many hybrids as Astilbe x arendsii, and the plants are generally smaller, reaching only 6 to 12 inches in height. Many bear foliage with bronze-tinged new growth. "Perkeo" and "Red Rog" bear dark pink to red plumes, while "Lilliput" and "Gnom" bear light pink flowers. "Snow Queen" bears snowy white plumes.
Astilbe Japonica Group
The Astilbe japonica group ranges in height from 2 to 3 feet. Both "Avalanche" and "Deutchland" bear creamy white flowers, but "Avalanche" has darker green foliage. "Koblenz" and "Dusseldorf" bear salmon pink flowers; however, "Dusseldorf's" flowers are darker pink. "Bonn" bears rose red flowers with a reddish tinge to the foliage, and "Bremen" has deep rose flowers.
Astilbe Simplicifolia Group
Plants in the Astilbe simplicifolia group reach about 12 to 18 inches tall, and the plumes tend to be narrower than those of other groups. "Hennie Graafland" and "Inshriach Pink" both bear clear pink flowers, however, "Hennie Graafland" has darker green foliage. "Aphrodite" and "Bronze Elegans" bear dark pink plumes. "Aphrodite" has a slightly more salmon tone, while the flowers of "Bronze Elegans" are rosy pink. Both have bronze-red foliage. "William Buchanan" is a dwarf that reaches only 8 inches in height and produces white plumes.