When considering astilbe (Astilbe spp.), many gardeners confine their use to moist, cool spots in shade. However, Chinese astilbe (Astilbe chinensis) and its cultivars, hardy in U.S. Department of Agriculture plant hardiness zones 3 through 8, stretch those limits with increased tolerance to both drought and sun. Chinese astilbe varieties expand the usefulness of this beautiful genus of plants and present colorful solutions to the challenges of dry shade gardens.
When discussing astilbe drought tolerance, the quality is relative to the tolerances and needs of other astilbe. Drought-tolerant astilbe and drought-tolerant desert plants have very different requirements. All astilbe thrive in consistently moist, well-drained soils. Even drought-resistant varieties still need regular watering and do best in moist spots protected from full sun. However, their adaptation to lower moisture, occasional drought and less shade makes them more suitable for general garden conditions and less susceptible to sun and drought damage than other astilbe species.
Differences between Chinese astilbe varieties and other less drought-tolerant astilbe are readily apparent to the eye. Many features appear stronger, sturdier, more durable and generally denser. The lacy leaves boast a thicker texture, as do the strong, sturdy stems. Even the flower plumes often exhibit greater density -- and increased fragrance -- than more drought-sensitive astilbe varieties. Chinese astilbe bloom later in summer, attract numerous butterflies and enhance bouquets with their longevity when cut or dried.
Although Chinese astilbe tolerate drought, uniform moisture in well-drained soils help these plants excel. Too much water, particularly in deep shade, leads to rot and premature death. Although more resilient and tolerant, Chinese astilbe foliage will brown and curl when exposed to frequent drought or too much sun. Like all astilbe, those damaged leaves will not recover. Promote new growth by removing affected leaves. Remove flower plumes after blooming or leave them over winter for ornamental interest and seeds for birds. Astilbe are not generally bothered by pests or any diseases of major concern.
Among the plentiful varieties of Chinese astilbe, some exceptional, dependable performers stand out. Pumila astilbe (Astilbe chinensis var. pumila) forms a fast-growing ground cover 6 inches high with lilac-pink flowers on 9- to 12-inch stems. "Visions" (Astilbe chinensis "Visions") beautifully enhances shade with 12- to 18-inch, raspberry-pink panicles above compact foliage mounded 9 to 12 inches high. Purple candle astilbe (Astilbe chinensis "Purpurkerze") shines with purplish-red flower plumes reaching 42 inches tall above a 24-inch mound of dark green leaves. These three drought-tolerant varieties are hardy in USDA zones 4 through 8.