Astilbe, also known as false spirea or meadowsweet, is a shade tolerant perennial suitable for many Iowa gardens. Most astilbe cultivars grow 2 to 3 feet tall although some varieties can grow to a height of 4 feet. The mid to dark green foliage is ternately compound (divided into 3 parts). Some varieties have a reddish-copper overcast to the foliage. The flower stalks are erect or arching panicles up to 2 feet long. Bloom occurs from early June through August depending upon the cultivar. Flowers are available in white and various shades of pink, red, or lavender. The genus Astilbe is composed of approximately 25 species. They are native to China, Japan, and Korea.
Astilbe grows best in light or partial shade. They require a consistent supply of moisture to prevent browning of the leaf margins. In extremely dry weather, the leaves may completely die if the plants are not watered. Astilbe also require well drained soils. They do not perform well in heavy, clay sites. At planting, work in peat moss or compost to aid in moisture retention and drainage. Mulching will also help retain soil moisture. Water new plantings regularly for the first two growing seasons. They require an inch of water per week. Fertilize in the spring with a slow-release fertilizer according to label directions. A fertilizer ratio of 3-1-2 is preferred. Astilbe chinensis cultivars are the most drought tolerant. Astilbe are quite pest- free. Although powdery mildew, wilt and spider mites have been reported, control is seldom necessary. In the landscape, astilbe usually need division every 4 years or so.
Astilbe can be combined with hosta, ferns, yews, and other shade tolerant plants. Their flower display will brighten dark areas of borders, fences, or walls. More commonly they are used as edging along stream beds or decorative water pools where partial shade and ample moisture, and adequate drainage are easily provided. They are also long lasting cut flowers for enjoying indoors. Some of the many varieties to choose from include:
|Variety||Height||Season of Bloom||Color|
|A. arendsii 'Bridal Veil'||18 inches||mid||white|
|A. arendsii 'Snow Drift'||24 inches||mid||white|
|A. japonica 'Deutschland'||24 inches||early-mid||white|
|A. arendsii 'Cattleya'||40 inches||late||rose|
|A. chinensis 'Finale'||19 inches||late||pink|
|A. chinensis 'Pumila'||16 inches||late||lavender|
|A. simplicifolia 'Sprite'||12 inches||mid||light pink|
|A. arendsii 'Etna'||24 inches||mid||dark red|
|A. arendsii 'Fanal'||24 inches||mid||red|
|A. japonica 'Red Sentinel'||22 inches||mid-late||scarlet red|
Gardeners are often looking for plants tolerant of shady sites.If your shady location has sufficient moisture or you are willing to provide the needed moisture during dry periods, astilbe is an excellent perennial choice.
This article originally appeared in the May 4, 1994 issue, p. 60.