The appeal of lavender, with its distinct fragrance and wide range of uses, makes it a highly desired garden plant. Many people attempt to cultivate this perennial herb, but growing it from seed is more difficult than propagating it from cuttings or established plants. Lavender seeds possess a natural dormancy mechanism that prevents them from sprouting immediately, which must be overcome for successful germination.
Essential Preparation: Cold Stratification
Lavender seeds require a specific pre-treatment known as cold stratification to break their natural dormancy. This requirement evolved to prevent germination during a warm spell in autumn, ensuring they only sprout after the danger of hard frost has passed in spring. Stratification simulates the natural winter cycle the seeds would experience outdoors, conditioning them for growth by exposing them to consistently cool, moist conditions.
Gardeners artificially stratify seeds by placing them in a sealed container with a damp medium, such as a moist paper towel, peat moss, or sand. The seeds must be kept moist but not saturated to prevent mold growth. The container is stored in a refrigerator, where the temperature remains consistently around 40°F (4°C). This chilling period must last for a minimum of four to six weeks, though some varieties benefit from up to eight weeks of cold exposure.
Optimal Timing for Indoor Sowing
The best time to sow lavender seeds is directly linked to the last expected spring frost date in your geographic location. The process starts with initiating the cold stratification treatment approximately eight to ten weeks before the final frost is anticipated. This duration accounts for the required chilling period and the subsequent germination time.
Sowing the seeds indoors should occur about six to eight weeks before the last expected frost date. This timing allows the slow-germinating seeds enough time to sprout and develop into small, sturdy plants before moving outdoors. While some gardeners attempt a “winter sowing” method, starting the seeds indoors offers significantly more control over the environment and generally results in a higher success rate.
Sowing and Initial Germination Conditions
When preparing to sow the stratified seeds, select a sterile, low-nutrient seed-starting mix, often mixed with sand or perlite to improve drainage. Shallow containers or seed trays are suitable, and the seeds should be sown directly onto the surface of the prepared mix. Lavender seeds require light to trigger germination, so they should not be buried deeply. Gently pressing the seeds into the surface or covering them with only a very fine layer of sand is sufficient.
The seeds require warmth to sprout after the cold treatment, ideally a consistent soil temperature between 70–75°F (21–24°C). Providing bottom heat using a specialized heat mat is often recommended to maintain this range and encourage germination. Maintaining high humidity is beneficial, which can be achieved by covering the tray with a clear plastic dome or plastic wrap. Consistent moisture must be delivered through misting or bottom watering, keeping the soil damp but never waterlogged.
Even with optimal conditions, germination can be slow and erratic, often taking between two to four weeks. Once the seedlings emerge, remove the plastic cover to increase air circulation and reduce the risk of damping-off disease. They must be placed under bright grow lights or in a sunny window to receive at least 12 to 16 hours of light daily to support healthy growth.
Transitioning Seedlings Outdoors
Once the lavender seedlings have developed their first set of true leaves and all danger of frost has definitively passed, they must be gradually introduced to the outdoor environment. This process, known as “hardening off,” prevents shock and damage to the fragile plants from sudden exposure to sun, wind, and temperature shifts.
The hardening off process should span seven to ten days before final planting. Begin by placing the seedlings in a sheltered, shady location for just one to two hours a day. Each day, the duration of outdoor exposure should be increased, and the amount of sunlight should be progressively intensified. By the end of the first week, the plants should be spending several hours a day in direct sun.
After this slow acclimatization, the lavender plants are ready for permanent transplanting into the garden. They should be placed in a location that receives full sun for most of the day and has exceptionally well-drained soil, as proper drainage is a significant factor in the long-term success of growing lavender.