Growing Astilbe in Iowa

While hostas are terrific plants for shady locations, a number of other perennials are wonderful additions to the shade garden. One of the best perennials for shade is astilbe, or false spirea. 

Astilbes have beautiful spike-like clusters of flowers that sway gracefully in the wind. Flower colors include white, pink, red, and reddish purple. The flowers are borne on stiff, upright or arching stems. Astilbe foliage varies from dark green to bronze. The astilbe's combination of colorful flowers and attractive foliage make it a perfect complement to the bold coarseness of hostas. Astilbes also make wonderful cut or dried flowers. Allow a few spent flower blossoms to remain on the plants in fall and you will be rewarded with elegant brown spikes through much of the winter.

Astilbes shine when many other shade loving perennials are waning. They bloom for 2 to 3 weeks. Depending on the variety, astilbes flower from early to late summer. Early blooming varieties begin to flower in late May or June while late bloomers begin in late July or early August. By selecting several varieties with different bloom times, the floral display can be extended over 2 or 3 months.

Astilbes also vary greatly in height. Some varieties like 'Sprite' or 'Perkeo' grow only 6 to 12 inches tall (bloom included), while 'Purple Lance' or 'Purple Candles' can reach 4 feet in height. This diversity in height makes astilbes versatile perennials well suited to many areas of the perennial border.

Growing Conditions

Plants grow best in part shade locations, and can do well in full shade, but may have fewer flowers.  Astible can also tolerate full sun if provided abundant moisture.

Fertile, moist, humus-rich soil is a must for these shade lovers. Astilbes are unforgiving in dry soils, as the leaves will brown quickly. Annual additions of compost or organic matter around the base of the plant will be rewarded with loads of blooms and healthy foliage. While astilbes require consistent moisture, they do not tolerate waterlogged or heavy clay soils well. Clay and poorly drained soils can be improved by incorporating peat moss, compost, or other types of organic matter into the soil before planting.

Propagation

Astilbes are easily propagated by dividing large clumps when the foliage emerges in early spring. Vigorously growing astilbes can be divided every 4 to 6 years After division, water and mulch well to aid establishment.

Species and Cultivars

Astibles are native to China, Japan, and Korea. There are 25 different species. Hundreds of hybrids or selections have been made from approximately a dozen species. 'Peach Blossom', the first cultivar introduced in 1903, is still available on the market today.

See the following chart for a listing of a few of the cultivars that are available.  Cultivars are listed by bloom time.

Looking for a Native Alternative?

Goat’s beard (Aruncus dioicus) is a similar looking plant to astilbe that grows in similar conditions.  A native of woodlands in eastern Iowa, goat’s beard
may grow 4 to 6 feet tall and 6 feet wide. Its pinnately compound leaves are 2 to 3 feet long. Dense spikes of creamy white flowers are produced in late spring/early summer (usually a little earlier than most astilbes). It prefers moist soils and partial shade. Because of its large size, goat’s beard is best used as a background plant or in the center of large beds.

More Information

• Perennials for Shade (publication)
• Perennials for Moist to Wet Soils
• Groundcovers for Shade

Photo credits: 1: mashiki/AdobeStock; 2: Aaron Steil; 3: Aaron Steil; 4: Tatiana/AdobeStock; 5: Michail/AdobeStock