Russian sage, or Perovskia, is an easy perennial shrub that requires minimal care but will reward you with attractive feathery bluish-gray foliage and soft blue flowering spikes in the late summer. The shrub prefers full sun, well-draining soil and little water, making it ideal for dry areas in your landscape and xeriscapes in USDA hardiness zones 4 to 9. Your Russian sage flowers on new growth and will be fuller and produce more flowers when you prune the shrub annually in the spring, while the plant is coming out of dormancy.
Look at each stem or branch of your Russian sage in the spring, after the last frost, when the new growth is beginning and can be identified easily. Russian sage blooms on new growth, and pruning your bush in the spring will promote more new growth and flowers.
Follow the branch or stem down, toward the base of the shrub, until you reach the third or fourth stem shoot.
Cut, or prune, the branch at the point of the third or fourth stem shoot. Make your cut at a 45-degree angle to promote the stem or branch to produce new stems for a fuller, more compact shrub. Older branches can be pruned to a height of 8 to 10 inches from the base of the bush to encourage new growth.
Cut 2 inches off the end of every other new growth stems when the stems have grown to around 18 inches long. By doing this extra trim, you will be encouraging additional new growth and flowering. Cutting every other stem will stagger the blooming of your Russian sage shrub so you have a longer bloom time.
Avoid unnecessary heavy pruning of your Russian sage shrub during the growing season of summer. Only prune dead, damaged or diseased stems and branches. Wait until spring to do any major shaping and pruning of the bush.