The 'Purple Cow' is a mid-sized variety that produces large clusters of purple blooms that will persist through the summer. It will reach 6-10' tall and 4-5' wide at maturity.
Chestnut Hill' is a more compact selection that will reach 4-5' tall and wide. It has a dense growth habit and makes for a great low-hedger. Stalks of fragrant, white flowers appear in spring.