Perovskia Blue Spire, or Russian Sage as its commonly known is a stalwart of the the perennial border. With its silvery green foliage, silver woody stems and purple flowers, Perovskia gives height and structure to the border.
Perovskia is also scented and is used as winter interest as you shouldn't cut the stems down until spring when the chances of frost are severely reduced.
It like Full Sun and a good well drained soil and should definitely be planted in volume for good effect.