Verbena bonariensis, commonly known as Tall Verbena or Argentinian Verbena, is a popular perennial flowering verbena. This plant has gained considerable popularity in garden design due to its unique architectural form and delicate, airy clusters of purple flowers. It creates a see-through effect in the garden, adding height and movement without blocking views of other plants. This South American native offers a long season of bloom and serves as a magnet for various pollinators.
Identifying Tall Verbena
Verbena bonariensis is recognized by several common names, including Tall Verbena, Argentinian Verbena, and Purpletop Vervain. This herbaceous perennial typically grows to a height of 3 to 6 feet, with a spread of 1 to 3 feet. Its distinct feature is its slender, wiry, and branching stems, which give the plant an open, airy appearance.
The plant’s small, vibrant purple to lilac flowers are grouped in tight clusters, usually measuring 2 to 3 inches in diameter. These fragrant blooms appear from early summer until the first frost, providing continuous color throughout the warmer months. While the stems are stiff and square, the foliage is sparse, primarily forming a rosette of deep green, lance-shaped leaves at the base of the plant. Verbena bonariensis is hardy in USDA Zones 7 through 11, and it often reseeds itself in colder climates where it is grown as an annual.
Growing Tall Verbena
Successful cultivation of Verbena bonariensis begins with selecting an appropriate site in the garden. This plant thrives in full sun, requiring at least 6 to 8 hours of direct sunlight daily for optimal growth and abundant flowering. While it can tolerate some partial shade, especially in hotter climates, full sun encourages a more robust and floriferous display.
Well-draining soil is a fundamental requirement for this verbena, as it dislikes soggy conditions that can lead to root rot. It is quite adaptable and can grow in a variety of soil types, including average to dry conditions, but performs best in loamy or sandy soils. Once established, Verbena bonariensis exhibits considerable drought tolerance, though consistent moisture, particularly during dry spells, promotes healthier growth and sustained blooming. The plant shows general resistance to most common pests and diseases.
Using Tall Verbena in Your Garden
The architectural form and airy texture of Verbena bonariensis make it an excellent choice for various garden designs. Its tall, slender stems allow it to be planted at the back of borders without overwhelming smaller plants, creating a layered effect. It is particularly effective in naturalistic plantings, cottage gardens, and meadow-style landscapes where its delicate appearance can soften more rigid structures.
Planting Tall Verbena in drifts or groups enhances its visual impact, creating a purple haze that adds depth and movement to the garden. Its “see-through” quality allows it to blend seamlessly with other perennials and grasses, providing vertical interest without blocking views. Beyond its aesthetic appeal, Verbena bonariensis is a superior nectar plant, attracting a wide array of pollinators, including butterflies, bees, and hummingbirds. This makes it a valuable addition to pollinator gardens.
Maintaining and Propagating Tall Verbena
Maintaining Verbena bonariensis is generally straightforward. While deadheading spent blooms is optional, it can encourage a longer flowering period and help manage the plant’s prolific self-seeding habit. Allowing the plant to go to seed will result in numerous volunteer seedlings, which can be either welcomed for naturalization or removed to prevent overcrowding.
In late fall or early spring, the stems can be cut back, though some gardeners choose to leave them standing through winter to provide habitat for native bees. In colder USDA Zones (below 7), Verbena bonariensis is often grown as an annual, but its self-seeding capability often ensures its return the following spring. For intentional propagation, seeds can be collected from mature flower heads in late summer or fall and stored for spring sowing. Seeds can be started indoors several weeks before the last frost or directly sown outdoors after the danger of frost has passed. Alternatively, stem cuttings can be taken.