Lemon Verbena (Aloysia citrodora) is a popular, fragrant deciduous shrub, native to South America, known for its strong, sweet citrus scent. It is cultivated globally for its aromatic leaves, used in culinary applications and teas, and its delicate white or pale lilac flowers. Gardeners often mistake its vigorous growth for an aggressive spreading tendency. Understanding the plant’s natural growth pattern is key to successful management.
Does Lemon Verbena Spread Via Roots?
Lemon Verbena does not spread aggressively through its root system and is not considered an invasive plant. It is a sub-shrub, meaning it develops a woody base but does not produce underground runners or rhizomes. The plant remains a single, clumping specimen, growing from a central root crown.
The root ball is confined and non-aggressive, similar to woody herbs like rosemary. Aloysia citrodora expands upward and outward from its established base. Any growth that appears to be “spreading” is the expansion of the shrub’s above-ground canopy, not subterranean roots pushing up new plants.
Understanding the Mature Growth Habit
Since the plant does not spread horizontally, its mature size is defined by its single, woody structure. In optimal, frost-free climates (USDA Zones 9 and warmer), Lemon Verbena can become a substantial, multi-stemmed shrub, reaching 10 to 15 feet in its native habitat.
In temperate climates, the shrub is typically smaller, often reaching 6 to 8 feet tall and wide when planted in the ground. When grown in a container, its size is naturally restricted, often maturing between 2 to 4 feet tall and wide. The ultimate height is also influenced by winter temperatures; in colder regions, the plant may die back to the ground annually, limiting its size and preventing the development of a large, woody structure.
Propagation Methods and Reseeding Potential
The primary way new Lemon Verbena plants are created is through taking cuttings. Both softwood cuttings (from new spring growth) and semi-ripe cuttings (taken later in summer) root readily. This ease of vegetative propagation is the most reliable method for gardeners to intentionally propagate the plant.
Natural reseeding is uncommon in most cultivated areas. Lemon Verbena produces small flowers from mid-summer to early fall, which can sometimes set seed. Successful germination and establishment from dropped seeds are rare, especially in regions with cool or short growing seasons. Any new plants that appear are typically volunteer seedlings, not root suckers, and can be easily identified and removed.
Controlling Size Through Pruning and Maintenance
Because Lemon Verbena grows vigorously and can become woody over time, regular pruning is necessary to maintain its shape and size. The most important pruning is a hard cutback performed in late winter or early spring, just before new growth begins. This annual rejuvenation prune involves cutting back the previous year’s growth by one-third to one-half.
This practice encourages the production of new shoots, resulting in a bushier, more compact plant. Pruning also helps prevent the plant from becoming an unmanageable thicket. Throughout the growing season, light pruning can be done to harvest leaves for culinary use and to keep the shrub tidy.