Astilbes for the Shady Garden

If ever a plant was given the wrong name, the astilbe would surely be the one. The name astilbe (a-STILL-be) means without brilliance, but a clump of astilbes in full bloom adds a radiant glow to any shady corner of the garden. The divided leaves are quite attractive and are mid- to dark green or bronze. They form interesting contrasts with larger-leaved hostas and complement the finely divided foliage of ferns. Individual flowers are small and insignificant. However, hundreds cluster together to form soft, feathery plumes that rise well above the foliage. Astilbes look their best planted in large drifts of a single color. In the perennial garden, they blend well with many other plants. If cut about halfway open, the flowers can be added to fresh bouquets and dry well for winter arrangements.

Astilbes are an easy-to-grow perennial, making few demands in the garden. They are quite content when given rich soil in partial to moderate shade. Adequate water is their only real need. If allowed to dry out, flowering is poor and the leaf edges turn brown, and under severe drought, many leaves die completely. Astilbes can grow in full sun but require watering more often. They thrive in the damp soil next to a pond.

Before planting astilbes in the garden, prepare the soil by working in some well-rotted compost or manure. Although the soil should be moist, it should not remain wet. Waterlogged soil can deprive roots of much-needed oxygen. After planting, astilbes do not need a lot of attention. A layer of mulch keeps the soil from drying out and holds down weeds. Working some compost or rotted manure into the soil around the plants each spring provides nutrients needed for flowering. Astilbes usually don't require division for several years unless additional plants are desired. Insects typically are not a great concern. Astilbes grow well in areas with high rabbit populations because rabbits don't find them very appetizing.

Several species of astilbe are available in catalogs and garden centers. Cultivars of the common astilbe (Astilbe arendsii) probably make up 90 to 95% of all astilbes sold. These plants grow about two to three feet tall and spread about two feet. The flowers appear in late spring, ranging from deep red to brilliant white, with many shades of pink, salmon, and magenta in between. 'Fanal', first sold in 1933, is one of the most popular cultivars. The deep red flowers glow against the bronze foliage.

The Chinese astilbe (A. chinensis var. pumila) is a dwarf variety that can be tucked in the front of the border. Because of its creeping habit, it is a good ground cover. Although this is one of the most drought-tolerant astilbes, flowering is best in moist soil. Flowers open in summer and last four to six weeks under favorable conditions. The one fault of the Chinese astilbe is that flower color is limited to rosy purple.

Another dwarf astilbe is the Star astilbe (A. simplicifolia). It grows 12 to 18 inches tall and is topped with panicles of white, rose, or salmon flowers at the end of July. The ornamental value of the Star astilbe continues after flowering, because the seed pods are quite attractive and persist well into fall.

The Fall astilbe (A. taquetti 'Superba') is just gearing up when the others are starting to fade. Flowers appear in late summer and continue through the first weeks of September. The fall astilbe is a vigorous grower; the lilac-purple flowers stretch up to four feet. If left on the plant, the decorative seed heads persist into winter. A continuous succession of flowers can be ensured by interplanting common astilbe with Chinese and Fall astilbe.

Astilbes are easily propagated by dividing the plants in the spring or fall. They will need additional watering until they reestablish themselves. Although dividing astilbes during the summer is possible, it should be avoided because the hot, dry weather greatly reduces the chances of success.

Astilbe can be started from seed with a little effort. The seeds require about four weeks of cold, moist storage to break dormancy. Many gardeners prefer to avoid the trouble and purchase roots or plants from a nursery or catalog. Hybrid cultivars especially should be purchased or propagated by division, because seed-grown progeny will not look like the parent plant.

For the true astilbe fan, winter forcing provides a way to extend enjoyment of astilbes. When dividing plants in the fall, a few extra can be potted. Keep them well watered and place them in a cold frame or protect with a layer of mulch. They need about three months of cold temperatures (<40oF) to set flower buds. After meeting the cold requirement, bring plants into the house and place in a sunny window. Fertilize lightly and keep well watered. Shortly, dazzling plumes of red, white, and pink can enliven a dreary winter day. The plants can be set out in the garden the following spring.

When given the proper conditions, astilbes prove to be tough, durable plants that can last for many years. Give them a try to add a splash of color to a shady part of your garden.