Lavender (Lavandula) is a fragrant perennial prized for its aromatic flowers. Propagating new plants from collected seed is an economical way to expand a garden, but requires understanding the precise timing and proper collection methods for a successful harvest. The process involves identifying mature seed pods, cutting the heads, separating the seeds from the plant material, and preparing them for a dormant period before planting.
Identifying Mature Seed Pods
The correct time to harvest lavender seeds is typically in the late summer or early fall, after the main flush of blooms has finished. To allow the seeds to develop fully, the flower spikes must remain on the plant until the vibrant purple color has completely faded and the entire spike appears dry and brittle. Visual cues indicate readiness: the spikes turn a dull, pale brown or gray, and the calyx holding the seed becomes hardened and darkened. If the spike is gently shaken and a few tiny, dark seeds fall out, the entire spike is ready for collection. Harvesting too early results in immature seeds with low germination chances.
The Physical Harvesting Process
The best time for collecting seed heads is mid-morning, after any dew has evaporated. Harvesting dry material is important because moisture can lead to mold during the subsequent drying phase. Use sharp, clean pruning shears or scissors to make a precise cut just below the dried flower head, leaving a short length of stem attached. Hold a container, such as a wide bowl or paper bag, directly underneath the spike as it is cut. This prevents mature, loose seeds from scattering onto the ground and minimizes loss.
Separating and Cleaning the Seeds
After harvesting, the seed spikes must be fully dried before the seeds can be extracted from the protective calyx. Spread the cut stems on a screen or hang them upside down in loose bundles in a cool, dark, and well-ventilated location for one to two weeks. This secondary drying period ensures all moisture is removed, which makes the seeds easier to release.
Once the spikes are completely dry, the seeds must be separated from the chaff using threshing and winnowing. Threshing is accomplished by gently crushing or rubbing the dried flower heads over a clean surface, freeing the tiny, dark, pepper-sized seeds from the brittle calyx structure. Winnowing removes the light, unwanted plant debris (chaff) from the heavier seeds. This can be done by carefully blowing across the collected material or using a fine-mesh sieve to separate the seeds from larger dried material. The seeds should be as clean as possible before storage to prevent mold growth.
Preparing Seeds for Storage or Sowing
Thoroughly cleaned lavender seeds are best stored in an airtight container, such as a small glass jar or a sealed plastic bag, to protect them from moisture and pests. The container should be clearly labeled with the lavender variety and the date of harvest. Optimal long-term storage involves placing the sealed container in a consistently cool, dark, and dry environment, such as a refrigerator, where seeds can remain viable for several years.
Lavender seeds have a natural dormancy that prevents them from germinating immediately. To overcome this, the seeds require a period of cold stratification before sowing to mimic the natural winter cycle. This process involves placing the seeds in a moist medium, such as a damp paper towel or sand, inside a sealed container. Refrigerate the container at 35 to 40 degrees Fahrenheit for approximately three to six weeks. Cold stratification breaks the dormancy and primes the seeds for successful germination when they are later sown indoors.