Argentinian Vervain

Also known as purple top, Verbena bonariensis is a tall, drought-tolerant, herbaceous perennial with a graceful, slender, branching habit, good grouped in a prairie planting or a sunny, dry traditional border, or scattered in a gravel planting. The slender, branching stems are sparsely clad with toothed, oblong, sage-green leaves, giving a transparent effect. From midsummer, and well into autumn, the stems are topped with round heads of light purple flowers, very attractive to bees and butterflies. Argentinian vervain provides dots of bright colour in a border or grassy planting, and holds the RHS Award of Garden Merit. In colder areas, protect existing plants with a winter mulch, but it will return anyway, as it seeds about mildly.