Set out plants in spring or fall, 15 to 18 inches apart. Astilbes prefer partial to full shade, but may be grown in sun in northern areas if particular attention is paid to maintaining a constant supply of moisture, especially early in the growing season. (Failure to do this will produce poor, chlorotic, unattractive foliage.) A soil well-enriched with organic matter is essential.
Astilbes are vulnerable to drought, and should be watered liberally; a year-round mulch will help retain moisture and moderate soil temperature. Other than that, and dividing established plants every few years, preferably in the fall, they are relatively care-free.
Their plumy inflorescences, even when dry, provide winter interest, so we suggest that they not be cut back until spring, prior to the onset of new growth.