Astilbes are elegant perennial garden plants with leaves that resemble those of the fern. Astilbes send up plumes of feathery flowers in pink, peach, red, violet or white in middle or late summer, depending on the variety. Even after blooming, the foliage and flower spikes remain decorative. All sizes are available, from dwarf forms for the front of the border to tall stately varieties. There are few plants which can bring so much color and presence to a shady area. Astilbe is also sometimes called false spirea.
Find a location with filtered or partial shade. Although they will tolerate full sun in colder climates, astilbe are generally happiest in partial shade.
If possible, find conditions that mimic the astilbe’s natural Asian habitat, where they grow along shaded stream banks. Moist soil is a must, but be sure that the plant's roots will not stand in water during the winter.
Before planting, amend the soil with organic matter. Astilbes require a rich fertile soil for best growth.
Plant crowns of the roots shallow, covering potential new shoots with only 1/2 inch of soil. Place smaller varieties 12 inches apart; larger varieties should be spaced 24 inches apart
If you desire to grow astilbe from seed, sow seeds indoors in the early spring, or right in the garden after the soil is warmed sufficiently.
Mulch after planting to retain soil moisture. Water new plantings well and monitor carefully until they are established.
Water frequently, especially during summer heat. Never allow astilbe to dry out or the foliage will crisp and eventually disappear. If plants do become dry and the foliage is unsightly, cut the plant to the ground to promote new growth.
Fertilize in the spring and again in the fall. Earlier-blooming astilbe form next year’s flower buds in the fall, so adding a high nitrogen fertilizer in October is beneficial.
Leave the flower spikes on the plant after it is finished blooming; deadheading is not necessary since it will not increase blooming and the dried seadheads are attractive. Save the dried flowers for indoor arrangements or crafts if desired.
Do not cut back the plant for winter because the old foliage serves to protect the plant from winter damage. Foliage can be cleared in the spring as new growth is emerging.
If you live in zones 3, 4 or 5, plant astilbe in the spring or in the fall, no later than the beginning of September. Planting late in the fall may cause small astilbe in particular to heave during freeze/thaw cycles. If astilbe crowns rise above the soil, gently press them back in.
Every three or four years, divide astilbe plants in the spring. They form large dense clumps and a knife or saw may be needed to split them.
Try partnering astilbe with other shade lovers like ferns and hostas. Because red, pink, salmon, lavender and white impatiens mirror the astilbe’s color varieties, they make a lovely combination in a lightly shaded spot. If you have the space, consider massing astilbes for maximum color impact.