Verbena bonariensis

This species is a tall, airy verbena from South America that is grown as a long-flowering perennial in warm zones or as a reseeding annual in colder areas. Plants send up wiry, see-through stems topped with small purple flower clusters that thread easily through mixed borders. The standout trait is its extended bloom that runs from summer to frost in full sun. It prefers well-drained soil and handles heat and periods of drought once established. In regions colder than zone 7 it rarely overwinters, but it often self-seeds and returns. Butterflies and hummingbirds visit the flowers throughout summer and fall.