Russian Sage (Perovskia) is a woody sub-shrub that produces flower spikes of:
blue
lavender and
lavender-blue.
The foliage is quite attractive and you are sure to like the finely cut gray-green narrow leaves.
Varieties mature in height from as little as two feet to as much as four feet with a spread of up to three feet.
Some cultivars have a tendency to flop over in the garden and thus can interfere with other ornamentals.
To prevent Perovskia from falling over you would be well advised to prune it back to about six inches in the spring and consider using peony hoops to help hold it in an upright position.
Family members Filigran and Longin have upright growth habits and therefore should be easier to control in the ornamental bed than the four foot tall variety Atriplicifolia.
Whatever variety that you choose you should have success with this perennial as the whole family will tolerate most soil conditions and will adapt to a wide range of ph values.
It is drought resistant so be sure not to over water any of the Perovskia family members.
Placement in full sun is advised for best results.