Mullein (Verbascum thapsus) is a common biennial plant recognized by its tall, fuzzy stalks. It produces a large quantity of very small seeds, often sought after for propagation. Successfully harvesting these seeds requires precise timing and careful technique to ensure viability. This guide provides steps for collecting and properly storing mullein seeds.
Identifying Ready Stalks and Optimal Timing
Mullein seed collection typically occurs in the late summer or early fall, after the plant has completed its flowering cycle. As a biennial, the tall seed stalk develops in the second year, rising from the basal rosette. The stalk transitions from green to a dry, uniform brown color, signaling that energy has been diverted to the seed capsules, indicating maturity.
Seed maturity is confirmed when the capsules feel completely dry and brittle. A simple test involves gently shaking the stalk; an audible rattle should be heard coming from the numerous small capsules. This sound confirms the seeds are fully developed, separated from the capsule walls, and dry enough for harvesting.
Harvesting seeds before they are fully dry and mature significantly reduces their viability and storage potential. The mullein plant produces hundreds of thousands of seeds per stalk, relying on wind and gravity for dispersal. Waiting for the entire stalk to brown maximizes the yield of robust, ready-to-store seeds before they are naturally released.
The Physical Collection Method
Prepare the necessary tools, which include sharp pruning shears, a paper bag or bucket, and gardening gloves. The fine hairs (trichomes) covering the mullein plant can cause skin irritation, making gloves a necessary precaution. Using a paper bag is preferable to plastic, as it allows for better air circulation and minimizes moisture buildup during transport.
The most efficient method involves cutting the entire seed stalk from the base using shears. Cut the stalk several inches above the ground to allow for natural seed dispersal from any remaining capsules. Carefully place the severed stalk, head-first, into the prepared bag or container to prevent premature seed loss.
Once the stalk is secured, the tiny seeds must be extracted from their protective capsules. A single mullein stalk can hold over 100,000 seeds, requiring careful handling to maximize the yield. This is done by gently bending and rubbing the stalk inside the collection bag, causing the dry capsules to break open and release the contents.
Alternatively, strip the seed pods off the main stem by hand, allowing the seeds to drop directly into the container. Care must be taken during this process, as mullein seeds are exceptionally small and can easily spill or be carried away by a breeze. Performing the stripping over a contained surface or inside a deep container ensures the maximum number of seeds are captured.
Post-Harvest Processing and Storage
Even if the stalks appear dry upon collection, the seed heads require a final drying period to ensure long-term viability. Spread the collected material in a thin layer on a screen or tray in a well-ventilated area, away from direct sunlight. Low humidity is beneficial during this time, which should last for several days to a week until all residual moisture is gone.
After complete drying, the seeds must be separated from the surrounding plant debris, known as chaff. Vigorously shaking the material or rubbing it against a fine mesh screen helps dislodge the seeds from the broken capsules. Using a small handheld sieve allows the tiny seeds to fall through while retaining the larger pieces of chaff.
Proper storage is necessary for preserving the seed’s genetic material over time. Mullein seeds should be placed in an airtight container, such as a glass jar or sealed plastic bag, and stored in a cool, dark location. Storing seeds at consistently low temperatures, ideally below 50 degrees Fahrenheit, can maintain viability for many years. Labeling the container with the collection date and species ensures accurate identification for future use.