Like all astilbes, Delft Lace Astilbe requires consistently moist soil and should not be allowed to dry out. Using 2-3 inches of mulch will help retain moisture, as will adding organic matter to the soil when planting. If planting on an eastern exposure with 4 hours of sun, more frequent watering may be required to prevent scorching.
While the flowers of Delft Lace Astilbe are excellent for cutting, this does not extend or improve the plant’s bloom period. Alternatively, you can leave the spent flower heads on the plant through winter for interest.
Astilbes, Delft Lace included, should be divided every 3-5 years as the clumps fill out. Division is most successful after the flowers have faded, but it is more important to adequately water the new transplants after division. Fertilizer is not typically necessary for the plant to do well.