Photo: Kew Gardens (flickr)
Verbena bonariensis is a tall, skinny, sun-loving annual verbena. Though it’s an annual in cold climates, it self-sows and comes back reliably each year, but it doesn’t seem to like staying in the same spot so much, as it hops around.
It is hardy to Zone 7 where it acts like a perennial. It can reach a height of five feet, but because it is so skinny it looks quite okay in the front of a bed, as one sees through it and past it to the plantings behind. It also puts out horizontal branches—but only a few—so that each plant looks a bit like a stick figure with arms and a small mop of lavender blooms on top, mimicking hair.
Because of its clusters of small lavender flowers, it pairs well with plants that have chartreuse foliage. It also looks good with perennials producing white or yellow flowers and shrubs that provide a dense backdrop for it. But it looks good just about anywhere!
Amsonia, for example, with narrow leaves and small blue blooms in the spring that give it the common name of bluestar, has bright yellow foliage in late fall. It provides a wonderful foil for skinny verbena, which keeps on producing masses of little lavender flowers right up to the fall frosts.
Remember, though, that self-sowing annuals like this verbena will not volunteer in a bed that has a heavy mulch.