Verbena is a widely cultivated flowering plant prized by gardeners for its extended blooming period, often lasting from late spring until the first frost. The genus includes hundreds of species and hybrids, displaying a variety of colors and growth habits. The common question of whether Verbena returns each spring stems from the fact that the term encompasses plants with significantly different cold tolerances. Whether a Verbena returns depends entirely on the specific type planted and the local climate conditions.
Understanding the Two Main Types of Verbena
The majority of Verbena varieties sold as bedding plants are categorized as tender annuals, meaning their entire life cycle finishes within a single growing season. These common garden favorites, often labeled as Verbena x hybrida, lack the genetic hardiness to survive freezing temperatures below ground. Once a hard frost penetrates the soil, the root systems of these plants die completely, requiring the gardener to replant them the following spring.
Other species, however, are true perennials and possess the biological mechanism to reliably return year after year. These types, such as Verbena canadensis (often called Rose Vervain), develop a crown and root structure capable of surviving dormancy through colder months. The above-ground foliage dies back, but the underground portion remains alive, ready to send up new growth when temperatures warm.
A third category includes species like Verbena bonariensis (Tall Verbena), which are often treated as annuals but frequently return through prolific self-seeding. While the parent plant may not survive the cold, it releases numerous seeds that successfully germinate in the same spot the following season. This natural propagation gives the illusion that the original plant has returned, providing a similar garden effect. The success of this self-seeding process depends on the plant’s ability to mature seeds before the first hard frost.
Factors Influencing Overwintering Success
Even for perennial Verbena types, survival is heavily dependent on the local climate, which is standardized by the USDA Plant Hardiness Zone system. A perennial variety must be rated hardy for the specific zone in which it is planted to stand a chance of surviving the minimum winter temperatures. If a perennial is planted outside its designated hardiness range, the extended periods of deep freezing will compromise the integrity of the root cells, leading to plant death.
Soil condition during winter often proves to be a greater challenge than temperature alone for perennial Verbena roots. These plants require well-draining soil, and prolonged exposure to cold, waterlogged conditions is highly detrimental. Poor drainage prevents oxygen from reaching the roots, resulting in anaerobic conditions and root rot, which can kill the plant even in moderate winter climates.
The specific location of the planting site can also create a localized microclimate that either aids or hinders overwintering success. Planting near a south-facing brick wall, for example, can increase the ambient temperature and soil warmth, offering a few degrees of protection. Conversely, areas exposed to consistent, harsh winter winds can experience greater desiccation and cold stress, reducing the plant’s chance of survival.
Techniques for Ensuring Verbena Returns Next Season
Gardeners can increase the odds of perennial Verbena survival, especially in zones at the colder edge of tolerance, by applying a protective layer of mulch. A thick blanket of organic material, such as straw or shredded leaves, should be spread around the plant crown after the ground has frozen. This insulation prevents repeated freeze-thaw cycles that can heave the root system out of the soil, exposing it to cold air and desiccation.
Proper preparation for dormancy involves timing the cutting back of spent foliage. It is advised to leave the old, dead stems and growth in place throughout the winter months. This material acts as a natural protective layer, trapping insulating snow and shielding the crown from winter elements. Pruning is best reserved for early spring.
For tender Verbena x hybrida varieties, propagation is the only way to ensure they return the following year. Gardeners commonly take stem cuttings from healthy plants in late summer, rooting them in a sterile medium before bringing them indoors to overwinter in a bright, cool location. Container-grown tender Verbena can also be moved to an unheated garage or basement once the foliage dies back, protecting the root ball from freezing.