Astilbe (Astilbe x arendsii) is a 1 1/2- to 3-foot-tall flowering perennial plant. Varieties such as ‘Fanal’ have lacy green foliage and deep red plume-shaped flowers. Other astilbe cultivars bloom in colors ranging from white to pink and lavender. Astilbes are frequently seen in shady areas of the garden, where they grow and spread in clumping mounds.
Astilbes thrive in U.S. Department of Agriculture plant hardiness zones 4 through 9. They die back each winter season and are pruned in October to November . They bloom mid-spring to summer and turn brown and leafless when the weather turns colder in late summer to fall, according to individual hardiness zone conditions.
These showy flowering perennials attract butterflies to the garden, tolerate deer and rabbits, and have the strong stalks needed for use as cut flowers. They do not have serious insect or disease problems.
Gather the equipment you will use to begin the pruning job.
Rake the dry foliage 1 foot away to give a clear view for pruning. The dried leaf material can be left on the ground to decompose over wintertime.
Make a sharp cut with the pruning shears on each dry stalk 2 inches above the plant base. Two inches is the approximate distance from the tip of the finger to the first knuckle.
Rake away and discard the cut stalks.
Clean the pruning shears with hot soapy water or an alcohol-soaked cloth. This prevents the possible spread of plant diseases.
The pruning job is now complete. If you look closely into the base of the plant you may see that new growth is already starting for next year. New growth first appears as hard green nubs between the dry stalks. The newly pruned plant will now have good air circulation and access to sunlight.
Pruning your astilbe yearly does not prevent growth and spread of the mound of underground roots. Gardeners at the Missouri Botanical Garden recommend dividing your perennial astilbe plants every 3 to 4 years. They are divided by root division in fall or early spring.