Lavender, a fragrant perennial from the genus Lavandula, is a popular garden shrub valued for its aromatic oil and purple flower spikes. Lavender plants are capable of producing viable seeds, and self-seeding does occur. However, the success and predictability of this process are highly dependent on the specific lavender species and the environmental conditions of the planting site. The resulting volunteer plants may not always be what the gardener expects.
Natural Seed Germination and Cultivar Purity
Self-seeding is sexual reproduction, which introduces genetic variability into the resulting seedlings. A volunteer plant will not be a clone of the parent, and its desirable traits like flower color or growth habit may differ significantly from the original cultivar. This loss of predictability is noticeable in hybrid varieties, such as Lavandin (L. x intermedia), which are often sterile or produce seeds that revert to parent characteristics. English lavender (L. angustifolia), by contrast, is more likely to produce seedlings resembling the parent, making it the species most often found self-seeding.
For a dropped seed to germinate, it must overcome dormancy. Lavender seeds typically require cold stratification—exposure to cold, moist conditions for several weeks to mimic winter. In a garden setting, this is achieved when seeds are exposed to winter temperatures and then warm up in the spring. Optimal soil temperatures for germination are between 65–75°F (18–24°C). Lavender seeds are minute and require light to germinate, meaning they must remain on or very near the soil surface rather than being buried deeply.
The Preferred Method: Vegetative Propagation
Due to the genetic uncertainty of seed propagation, most commercial growers and home gardeners rely on vegetative methods to multiply their lavender stock. This asexual reproduction, primarily through cuttings or layering, creates an exact genetic copy, or clone, of the parent plant. This guarantees that desirable characteristics, such as specific color or compact growth habit, are preserved in the new plant.
The most common technique involves taking stem cuttings from the parent plant. Softwood cuttings, taken from flexible new growth in late spring or early summer, root quickly. Semi-hardwood cuttings, taken from more mature growth later in the season, are also effective. Cuttings are typically dipped in rooting hormone to stimulate root development before being placed in a well-draining medium.
An alternative method for propagation is layering, which encourages a branch to root while still attached to the main plant. A low-lying stem is bent to the ground, lightly scored, covered with soil, and held in place. Once the buried section develops roots, the new plant is severed from the mother plant and transplanted. This process is reliable and avoids the genetic risks associated with seed production.
Encouraging or Preventing Volunteer Plants
Gardeners can influence the probability of self-seeding based on pruning habits. To prevent unwanted volunteer seedlings, deadheading is employed, which involves removing spent flower stalks before the seeds fully mature and drop. Timely deadheading stops seed production and redirects the plant’s energy toward producing a potential second flush of blooms, often seen in English lavender varieties.
If the goal is to encourage self-seeding and allow volunteer plants to appear, avoid deadheading the first flush of flowers. Allowing the flower heads to dry fully on the plant permits the seeds to ripen and naturally scatter across the soil. Minimal soil disturbance around the parent plant is beneficial, as the tiny seeds require light to germinate and can be easily buried too deeply by tilling or heavy mulch. Seedlings that emerge will need to be thinned out to prevent overcrowding and ensure adequate airflow for the mature parent plant.