Verbena bonariensis is a perennial herb in the verbena family, native to South America. It is widely cultivated as an ornamental plant in temperate regions, and has become naturalized in many places. It grows to 1–3 m tall, with erect stems that are slender, much-branched, and covered with small, stiff hairs. The leaves are opposite, ovate to lanceolate, 3–8 cm long and 2–4 cm broad, with a toothed margin. The flowers are produced in clusters of 3–6 at the end of each stem, each flower 5–8 mm diameter with five purple petals. The fruit is a small capsule containing numerous tiny seeds.

Verbena bonariensis is a popular garden plant, grown for its tall, airy stems bearing clusters of small purple flowers from summer to autumn. It is best grown in full sun in a well-drained soil, and tolerates a wide range of soil types including heavy clay. It is drought-tolerant, but benefits from regular watering in dry periods. It is short-lived, typically only lasting 2–3 years, but self-seeds readily to maintain itself in the garden.

The main pest and disease problems are powdery mildew and aphids. It readily reseeds, so don’t worry too much about its problems. You’ll see it again next year.