Common Name: astilbe
Type: Herbaceous perennial
Family: Saxifragaceae
Zone: 3 to 8
Height: 1.50 to 2.00 feet
Spread: 1.00 to 1.50 feet
Bloom Time: June to July
Bloom Description: Red
Sun: Part shade to full shade
Water: Medium
Maintenance: Low
Flower: Showy, Fragrant
Tolerate: Rabbit, Deer, Heavy Shade, Black Walnut
Culture
Easily grown in average, medium moisture, well-drained soils in part shade to full shade. Prefers moist, humusy, organically rich soils. Soils must not be allowed to dry out. If regularly watered, foliage will usually remain attractive throughout the growing season. A summer compost mulch helps retain soil moisture. Removing faded flower stalks will not prolong bloom but may improve plant appearance, particularly if a ground cover look is desired. On the other hand, many gardeners leave the flower stalks in place after bloom because of the continuing ornamental interest of the dried seed heads. Divide clumps when overcrowding occurs (every 3-4 years).
Noteworthy Characteristics
Astilbe is a genus of around 20 species of clump-forming, herbaceous perennials native to eastern Asia and eastern North America. Plants are characterized by graceful, fern-like mounds of mostly basal, 2-3 ternately compound leaves, usually with sharply-toothed leaflets, and tiny flowers densely packed into erect to arching, plume-like flower panicles rising above the foliage on slender, upright stems.
Genus name comes from the Greek words a meaning without and stilbe meaning brightness in reference to the dull leaves of some species.
'Radius' is a red-flowered cultivar that typically grows to 26" tall and to 20" wide. It is sometimes sold by nurseries as an Astilbe x arendsii hybrid. It features an attractive foliage mound of compound, dark green leaves with sharply-toothed leaflets. Leaves are tinged with red as they emerge in spring. Tiny, slightly fragrant, bright red flowers in airy, erect to arching, densely packed branched panicles bloom above the foliage on slender, upright burgundy stems from late spring to early summer (June-July).
Problems
Foliage decline (leaves brown up) may occur in hot summers and/or periods of drought if soils are not kept moist. Powdery mildew and wilt may appear. Japanese beetles may chew on the foliage. Deer and rabbits tend to avoid this plant.
Uses
Mass or group in shade gardens, woodland gardens and shaded areas of border fronts and cottage gardens. Excellent ground cover or edging plant for shady areas. Also effective on pond or stream banks. Foundations.