The genus Verbena encompasses a diverse group of popular flowering plants, known for their extended bloom period and vibrant color range. These plants are frequently used in garden beds, containers, and hanging baskets. The question of how tall Verbena grows does not have a single answer, as the mature size varies dramatically across the many species and hybrid cultivars available. Understanding the genetic potential of a specific type is the first step for a gardener planning a landscape, as height is based on whether the plant will form a low mat or an upright structure.
The Range of Verbena Heights
The mature height of a Verbena plant is primarily determined by its genetics, leading to a wide spectrum of sizes. The range extends from low-growing groundcovers that barely reach six inches to towering specimens that can exceed five feet. Trailing or low-mounding varieties, often hybrids (Verbena x hybrida), are commonly used in containers and as bedding plants. These types typically mature at a height of 6 to 12 inches but can spread widely, sometimes reaching two feet or more in width.
Conversely, the upright or stiff-stemmed Verbena types contribute vertical interest to a garden design. A prime example is Verbena bonariensis, sometimes called tall verbena or purpletop vervain. This species commonly reaches heights between 4 and 6 feet, with clusters of small flowers appearing at the top of the stalk. Other taller, native species, like Blue Vervain (Verbena hastata), can also grow to a height of 3 to 5 feet, resembling the stature of V. bonariensis.
Environmental Factors Influencing Maximum Growth
While the potential height is set by the plant’s DNA, external environmental conditions dictate whether the Verbena will reach that maximum potential. Sunlight exposure is a major requirement, as Verbena plants thrive when they receive full sun, ideally a minimum of six to eight hours per day. Insufficient sunlight often leads to etiolation, where the plant stretches weakly toward the light source. This results in spindly stems that may be taller but lack the rigidity and density of a sun-grown specimen.
Soil composition and moisture levels also influence final size. Verbena requires well-drained soil and prefers lean, even slightly sandy conditions, as they are susceptible to root rot in soggy environments. While established plants are notably drought-tolerant, prolonged periods of excessive dryness can stunt growth and reduce the vigor necessary for height development. Furthermore, temperatures affect the rate of stem elongation; cooler temperatures (50 to 60 degrees Fahrenheit) slow the growth rate, resulting in a more compact plant, while warmer conditions accelerate the process.
Managing Verbena Size
Gardeners can actively manipulate the growth habit of Verbena to control its size and shape. A technique called “pinching” or “tipping” is particularly effective when the plant is young. Removing the very tip of a young stem encourages the plant to divert growth hormones to the lateral buds, promoting denser, bushier growth rather than vertical elongation. This action results in a shorter, fuller plant that often produces more flowers.
Regular deadheading, the removal of spent flower clusters, helps manage size and maintain plant health. Deadheading prevents the plant from expending energy on setting seeds, redirecting that energy into new vegetative growth and subsequent flowering. If a Verbena begins to look “leggy” or its bloom production slows down during mid-summer, trimming the entire plant back by up to one-fourth of its height can stimulate a flush of new, more compact growth and a renewed cycle of blooming. The size of the container also acts as a physical limitation; Verbena grown in a small pot will be restricted in both root and canopy development, resulting in a smaller overall plant compared to one grown directly in the garden soil.