Astilbe is a popular perennial shade plant known as False Spirea and is often grown for its beautiful plumage-like flowers and fern-like foliage. It grows well along the sides of creeks and ponds where there is not full sun. Some varieties will grow more than 5 feet tall with graceful purple, white, pink or red flowers. Typically, it is propagated by division of the roots in early spring. Many nurseries will sell it during this time in the bare root stage, which simply means it has been cleaned of the soil it grew in and is ready for planting immediately.
Remove the Astilbe from the paper or packaging it was wrapped in for transport. Hopefully, it is still moist, or you may have dead roots on your hands. Place the roots into a bucket of water to hydrate them for a couple of hours before planting. Since Astilbe likes the warmer temperatures, transplant it once the soil has warmed to about 50 degrees. If you received the plant before the soil has warmed, keep it in a cool place, laying on its side covered in moist soil, until the soil warms
Dig up the soil where you want to plant them. Work some well-rotted compost into the soil to give it more nutrients and to improve the drainage. Astilbe likes a moist soil, so the more plant matter, the better moisture retention. You could add some moistened peat moss if the soil is heavy.
Dig a hole for the roots just a few inches deep so that the crown of the plant is just below the surface of the soil. If you see any side shoots coming out, cover them with just a half an inch of soil. Pat the surface of the soil down so that it settles around the newly planted roots. If the plant has already started growing, be careful not to break off the new shoots.
Water the area well after planting and then anytime the soil is dry while the plant is young. After a year or two, it will be such a large plant that it should not need extra watering, especially if you don't plant it in too much sunlight.