Lavender, a beloved herb prized for its fragrance and beauty, can be rewarding to grow from seed, but it often presents a challenge. The key to successful germination is cold stratification. This preparatory process breaks the seed’s natural dormancy, dramatically increasing the sprouting rate compared to planting seeds directly into warm soil. Applying this chilling period gives lavender seeds the best possible start toward becoming fragrant, mature plants.
Why Lavender Seeds Require Cold Treatment
Lavender varieties, particularly common English types, are native to regions with cold winters. Their seeds evolved a survival mechanism called dormancy, a physiological state that prevents premature sprouting during warm autumn spells. Dormancy is maintained by a hard seed coat and internal chemical inhibitors.
Cold stratification mimics the natural winter environment, signaling to the seed that spring is approaching. The combination of cold temperatures and constant moisture softens the seed’s outer shell, allowing water and oxygen to penetrate. Simultaneously, the chilling period breaks down germination-inhibiting hormones. Without this simulated winter, a significant number of seeds remain dormant, leading to a very low germination rate.
The Practical Guide to Cold Stratification
To artificially induce winter conditions, expose the seeds to cold, moist temperatures just above freezing. The recommended time frame for cold stratifying most lavender seeds is typically 3 to 6 weeks. The ideal temperature range for this chilling period is between 35°F and 40°F (2°C to 4°C), which is the standard temperature inside a household refrigerator.
A common and reliable method uses a damp medium like a paper towel, fine sand, or vermiculite. For the paper towel method, lightly moisten the towel until it is damp but not dripping wet. Spread the seeds across one half and fold the other half over them.
Place the folded paper towel inside a sealed plastic bag or container, labeling it with the variety and start date. The sealed bag maintains high humidity, and the refrigerator provides the consistent cold temperature needed. Check the bag weekly to ensure the paper towel remains moist and to look for mold, misting with water if the medium dries out. Most common lavender types require the full chilling period for reliable results.
Transitioning Stratified Seeds to Soil
Once the cold stratification period is complete, the seeds are primed and ready for germination. Immediately following the chilling process, the seeds need warmth and light to signal the start of spring growth. Use a well-draining seed starting mix in shallow trays, as lavender seedlings are susceptible to root rot in overly saturated soil.
Lavender seeds need light to germinate, so they should be sown very shallowly, often just pressed onto the surface of the moist soil. If covering them, use only a light dusting of vermiculite or sand, no more than 1/8 inch deep, to anchor the seeds without blocking the necessary light. The ideal temperature for germination is significantly warmer than stratification, typically ranging between 65°F and 70°F (18°C to 21°C).
Placing the trays on a heat mat set to a consistent temperature can help expedite the process, especially if the ambient room temperature is cooler. Ensure the seedlings receive ample light, such as from a south-facing window or a grow light positioned a few inches above the trays, for 12 to 18 hours per day. Even after stratification, germination can take anywhere from 14 to 28 days, requiring consistent moisture and patience for the tiny seedlings to emerge.