Verbena bonariensis, Purpletop Verbena is a well-known garden favourite, a herbaceous perennial growing its light airy stalks to 2m and more atop with its distinctive purple flowers that attract bees and other pollinators all summer long. It self-seeds prolifically and this can be easily managed by dead-heading some of the flowerheads. In colder regions or in exceptionally cold winters it may not make it through and can be treated as an annual that self-seeds.