Verbena is a popular flowering plant prized for its long-lasting, vibrant blooms that appear from late spring until the first hard frost. These plants offer a wide array of colors, making them a fixture in flower beds and container arrangements. The foliage is often dark green with a lanced shape and toothed edges, providing a textured backdrop for the clusters of small, star-shaped flowers. The classification of this plant is often confusing because its life cycle varies significantly depending on the specific type and the environment in which it is grown.
The Determinant of Verbena’s Longevity
The answer to whether a Verbena is an annual or a perennial is not straightforward, as the classification is determined by the specific plant species and the local climate. An annual completes its life cycle—germinating, flowering, and setting seed—within a single growing season before dying. A true perennial lives for more than two years, typically returning each spring after the winter dormant period.
The primary environmental factor influencing Verbena’s survival is the temperature extremes of the winter season, which is mapped out by the USDA Hardiness Zones. Many species of Verbena are naturally perennial, but they are considered “tender perennials” because they only tolerate the mild winters found in warmer regions, generally zones 8 through 11. In these areas, the plant will reliably return year after year.
Gardeners in colder climates (zones 7 and below) must treat these same tender perennial varieties as annuals, replacing them each spring. The plants lack the necessary cold hardiness to survive a sustained period of freezing temperatures. Furthermore, a substantial number of modern, compact garden Verbenas are specifically bred as hybrids (Verbena x hybrida) for intense, season-long flowering, meaning they are cultivated and sold exclusively as annual bedding plants regardless of the local climate.
Defining Common Verbena Varieties
The diverse Verbena genus includes several types that illustrate the differences in longevity and growth habit.
True Perennials
True perennial Verbenas, such as Blue Vervain (Verbena hastata), are highly cold-tolerant and reliably return in colder zones, sometimes as low as USDA zone 3. This type of Verbena is typically an upright, tall plant, often reaching several feet in height with distinct spikes of flowers.
Tender Perennials
Other species are classified as tender perennials, like Tall Verbena (Verbena bonariensis), which is generally hardy in zones 7 through 11. This variety is known for its airy, tall stems, which can grow to six feet, topped with purple flower clusters. While it dies back in colder zones, V. bonariensis often self-sows readily, meaning new seedlings frequently appear the following spring, leading to the mistaken impression that the original plant survived.
Hybrid Annuals
Many low-growing, trailing varieties popular in containers and hanging baskets are Hybrid Verbenas (Verbena x hybrida or Glandularia x hybrida). These hybrids are bred for a dense, mounding habit and continuous, colorful blooming. They are overwhelmingly cultivated and discarded as annuals after one season, providing immediate, non-stop color until the first frost.
Cultivation and Seasonal Maintenance
Successful cultivation requires the plant to receive sufficient light throughout the day. Verbena requires at least six to eight hours of direct sunlight daily to produce a continuous display of blooms. Full sun exposure is also important for maintaining good air circulation around the foliage, which helps prevent powdery mildew.
The soil structure is important for the plant’s health, as Verbena needs a well-draining medium that prevents the roots from sitting in standing water. Once established, the plant exhibits drought tolerance, requiring less frequent watering than many other flowering annuals. Regular watering is still necessary, especially for container plants, but the soil should be allowed to dry slightly between applications.
To promote continuous flowering and prevent the plant from putting its energy into seed production, a process called deadheading is beneficial. Removing the spent flower clusters encourages the plant to produce new buds and maintain a tidy appearance. Gardeners who wish to attempt overwintering perennial types in zones colder than their hardiness rating can apply a thick layer of organic mulch around the base of the plant in late autumn. This insulating layer helps protect the crown and roots from severe temperature fluctuations, increasing the odds the plant will resprout when the spring season arrives.