Yarrow (Achillea millefolium) is a hardy perennial herb recognized for its fern-like foliage and flat-topped clusters of flowers. This resilient plant is a popular addition to perennial borders and meadows, thriving in diverse conditions. Propagating yarrow by saving seeds from existing plants is a rewarding and cost-effective method to ensure a continuous supply for future seasons. The process requires careful timing during collection, effective separation of the tiny seeds, and appropriate storage to maintain viability.
Knowing When to Harvest
Timing the harvest correctly is essential for collecting viable seeds for the next growing cycle. Yarrow seeds must reach complete maturity while still attached to the plant; harvesting too early yields immature seeds that will not germinate.
The visual indicator for maturity is the complete transformation of the flower cluster, or inflorescence, from its fresh color to a dried, brittle brown. This change typically occurs late in the growing season, usually in late summer or early fall. The entire flower head should appear fully desiccated, feeling dry and crumbly to the touch.
Collecting the Seed Heads
Once the flower heads have turned brown and are visibly dried, begin collection. Use sharp scissors or pruners to cut the entire seed head, or umbel, along with several inches of the attached stem. Collecting a portion of the stem helps keep the heads together for subsequent drying and processing steps.
Place the collected heads into a large paper bag or bucket immediately upon harvesting. This helps capture any loose seeds that may detach during cutting, preventing unnecessary loss. After harvesting, the material must undergo a final, thorough drying period of one to two weeks in a dark, dry, and well-ventilated room to ensure all moisture is removed before cleaning.
Separating Seeds from Chaff
The process of separating the small, dust-like seeds from the dried plant material, or chaff, is divided into two steps: threshing and winnowing. Threshing involves breaking apart the dried flower heads to release the seeds from their protective casings. This can be accomplished by rubbing the dried heads vigorously between your hands over a container or by gently crushing them with a rolling pin on a tarp.
Once the material is crushed, winnowing uses air movement to separate the lighter chaff from the heavier seeds. Because yarrow seeds are notably small, resembling fine specks, a gentle air source is necessary. You can use a shallow tray and gently blow across the mixture, allowing the lighter debris to lift and fall away while the heavier seeds remain. Alternatively, a box fan set to a very low speed can provide a controlled stream of air, allowing you to slowly pour the seed-chaff mixture in front of it to isolate the clean seeds.
Ensuring Long-Term Seed Storage
For long-term viability, yarrow seeds must be completely dry before sealing them away for storage. Excess moisture is the primary cause of seed degradation, as it can trigger premature germination or encourage mold growth. The ideal moisture content for most seeds, including yarrow, is generally below 8 percent for successful preservation.
After cleaning, place the dry seeds into an airtight container, such as a glass jar, or in a breathable container like a paper envelope. If using a jar, ensure it is completely sealed to prevent moisture from the air reaching the seeds. The best storage environment is consistently cool, dark, and dry, with a refrigerator being an excellent option to slow the seeds’ metabolic rate. Always label the container clearly with the species name, Achillea millefolium, and the date of harvest to track the seeds’ age and viability.