Verbena bonariensis: a see-through plant that enlivens the summer garden

Verbena bonariensis, aka purpletop verbena, is a tall, airy plant with clusters of two to three-inch purple flowers on long, airy stems that bloom mid-summer till frost. It is particularly effective at adding see-through "exclamation points" to the perennial border. Butterflies love its nectar, and when the flowers turn to seeds, the goldfinches arrive in flocks. This low-water plant grows three to six-feet tall and spreads one to three feet. Thanks to its stiff stems, Verbena bonariensis usually stays relatively tidy and upright.

This plant is native to Brazil and Argentina and was first grown as a garden ornamental in 1726. It is a perennial in California's mild climate zones, where it has naturalized in some areas. Although it may spread in the garden, it typically does not create a problem. As a precaution, keep garden soil mulched to help avoid a proliferation of volunteer seedlings.

Verbena bonariensis looks great in the middle of the border, especially in cottage gardens and other low-water landscapes where flowers are loved but excessive water use is not. The flowers are visually striking among yellow, orange, and pink-blossomed companions. The long-lasting cut flowers make a lovely addition to floral arrangements. This plant is a recipient of England's Royal Horticultural Society Floral Committee's Award of Garden Merit due to its "attractive flowers and uncluttered habit."

Purpletop verbena is easy to grow in sunny, well-draining gardens from seed or from transplants. If transplanting, water well to get it established. After that, it is fairly drought tolerant. Although it's not picky about soil, it will grow best in fertile soil high in organic matter. Other than powdery mildew, which does not reduce its flowering ability, Verbena bonariensis has few pest or disease problems.