Lavender (Lavandula) is a fragrant, woody sub-shrub prized for its color and aroma. Gardeners often wonder if this perennial spreads aggressively. Lavender is not considered invasive or an aggressive spreader like mint or bamboo. Its expansion is predictable and manageable, occurring through two distinct, non-aggressive mechanisms that determine its size and where new plants may appear.
How Lavender Naturally Expands (Mounding vs. Runners)
Lavender expands through basal growth, resulting in a characteristic mounding shape. The plant grows outward and upward from a central, woody base that widens over time. Different varieties, such as compact English lavender (L. angustifolia) or larger Lavandin hybrids (L. x intermedia), have different mature sizes, which affects the final mound diameter.
Lavender does not spread using underground runners, technically known as rhizomes or stolons. Plants like mint use these specialized horizontal stems to send new, genetically identical shoots far away from the parent plant. Lavender lacks this aggressive vegetative expansion method, meaning the main plant will simply become a larger, denser mound. The perceived “spread” is usually just the mature diameter of the single plant, which for some vigorous hybrids can reach three to four feet wide.
The Role of Self-Seeding in New Growth
The second way lavender multiplies is through sexual reproduction via seed drop, commonly called self-seeding. After the blooms fade, the plant produces small seeds that drop near the parent plant, leading to new seedlings in the vicinity. This is usually a manageable process and not the same as aggressive, runaway spreading.
The success of self-seeding depends heavily on the specific variety and the environmental conditions. Many cultivated hybrids are sterile or weak self-seeders. However, some species readily drop viable seeds, especially in hot, arid climates that mimic their native Mediterranean habitat. Factors like minimal soil disturbance and the presence of gravel mulch, which provides excellent drainage, can encourage successful germination of these dropped seeds. While a few new plants may appear, they seldom emerge in the overwhelming numbers associated with truly invasive species.
Controlling Lavender Size and Spread
Managing lavender’s size requires proactive maintenance, primarily through regular pruning, to maintain a dense, compact shape. Pruning prevents the plant from becoming excessively woody and sprawling. The necessary pruning should be performed annually, typically after the main flush of blooms has faded.
When pruning, cut back the green, leafy growth but avoid cutting deep into the old, woody stems, as lavender often does not regenerate from this old wood. A good practice is to cut back about one-third of the plant’s height, shaping it into a neat, rounded mound. This action stimulates new growth and ensures the plant remains vigorous and full rather than becoming leggy and sparse.
To prevent the appearance of unwanted new seedlings, a simple technique called deadheading is highly effective. Deadheading involves removing the spent flower stalks before the seeds have a chance to fully form and drop to the ground. By removing the seed source, gardeners can completely control where and when new lavender plants appear. This combination of annual shaping and bloom removal ensures the plant stays in its intended spot and size.