Verbena Bonariensis (purpletop vervain, tall verbena, clustertop vervain, or pretty verbena) Desrving of its popularity. It makes an architectural statement with slender, willowy stems that stand up to 6' tall and do not need staking. It then branches out widely near the top where rich lilac-purple flower clusters stand alone, as if they are floating. Makes a great see-through plant. Winter hardy to Zones 7-10 grow in average, moist, well-drained soils in full sun to part shade.