Green onions, often called scallions, are a common garden crop and a perfect entry point into saving seeds. This process allows gardeners to ensure a continuous supply of their favorite Allium variety without needing to purchase new stock annually. To produce viable seeds, the plant must complete its natural life cycle, which involves “bolting,” where it develops a flower stalk. Understanding this process allows gardeners to easily harvest and preserve the small, black seeds for future planting.
Preparing the Plant for Seed Production
Green onions are typically biennials, meaning they grow foliage in the first year and produce seeds in the second year after overwintering. For successful seed saving, selected plants must remain undisturbed through their second season to shift from vegetative growth to reproductive growth. This transition is marked by the plant sending up a tall, rigid, central stalk, which culminates in a dense, spherical flower cluster known as an umbel.
Select the healthiest, most vigorous plants for seed stock, ensuring they exhibit the desired characteristics of the variety. Once selected, all harvesting of green foliage must cease, allowing the plant to direct energy toward the developing umbel. The immature flower head opens, displaying small, white flowers that are pollinated by insects, leading to the formation of small, green seed capsules.
Seed maturation is indicated by the umbel drying and browning over several weeks. The capsules transition from green to a papery, light tan or brown color. Black seeds may become visible as the capsules begin to split open. Monitor the umbels closely at this stage, as waiting too long can result in the seeds shattering and falling to the ground before collection.
Collecting the Seed Heads
Collection must be timed carefully to capture the maximum number of mature seeds while minimizing loss from shattering. Harvest should occur on a dry, windless day, ideally in the late morning after any dew has evaporated. Dry conditions are necessary because moisture is detrimental to seed viability and storage.
To prevent ripe seeds from scattering, carefully slip a paper bag or clean cloth sack over the umbel before snipping the stalk. Use sharp shears to cut the woody stalk several inches below the seed head, leaving a short handle. This technique ensures that any loosened seeds are contained within the bag during cutting.
The collected seed heads, still attached to their stalks, should then be moved to a sheltered, dry location for a final curing stage. Spread the stalks on a screen or hang them upside down in a brown paper bag in a warm, low-humidity area, such as a garage or attic. This allows the remaining immature seeds to fully dry and release from their capsules. This curing period typically lasts between one and two weeks until the umbels are completely brittle.
Cleaning and Storing the Seeds
Once fully dried, the seed heads need to be processed to separate the seeds from the surrounding plant debris, known as chaff. This initial process, called threshing, involves gently crushing the dried umbels by hand or rubbing them over a fine mesh screen to break open the papery capsules and release the small, black seeds. A substantial amount of chaff, including dried flower parts and capsule fragments, will be mixed with the seeds at this stage.
The next step is winnowing, which separates the relatively heavy seeds from the lighter chaff. This can be accomplished by carefully pouring the seed-chaff mixture from one container to another in front of a gentle fan or on a day with a light breeze. The current of air will carry the lighter debris away, while the heavier seeds fall straight down into the collection container. This process may need to be repeated multiple times to achieve a clean sample.
The resulting seeds must be absolutely dry before being placed into long-term storage to prevent mold and premature germination. They should be stored in an airtight container, such as a glass jar or a sealed plastic bag, or a breathable container like a paper envelope. The container must be clearly labeled with the green onion variety and the year of harvest. Storing the seeds in a consistently cool, dark, and dry environment, such as a refrigerator or a dedicated storage area, will maintain their viability for up to two years.