Saving seeds from your garden is a rewarding practice that connects one season to the next. Radishes are excellent candidates for this process, offering a straightforward path to generating your own supply for future plantings. Radish plants produce abundant seeds, making them a great choice for beginning seed savers. Cultivating radishes for seed requires allowing the plant to complete its full reproductive cycle.
Allowing Radishes to Bolt for Seed Production
Radish plants, typically grown as cool-season crops, must undergo “bolting” to produce seeds. Bolting is the plant’s shift from vegetative growth (developing the edible root) to reproductive growth (sending up a tall flower stalk). This transition is triggered by environmental stress, usually high temperatures (exceeding 80°F) and longer daylight hours. When conditions become unfavorable, the plant moves quickly to propagate the next generation.
Once a radish plant bolts, its root becomes woody, bitter, and inedible because the plant redirects stored energy into the flowering shoot. The plant develops small, four-petaled flowers, usually white or purple, which are pollinated by insects. Following pollination, the flowers produce elongated, green seed pods along the stalk. Most common spring radishes are annuals and bolt in a single season. Larger varieties, like daikon or winter radishes, can be biennials, sometimes requiring cold exposure before flowering and setting seed in their second season.
Recognizing When Seed Pods are Ready for Harvest
The green seed pods (siliques) mature slowly on the tall stalk. These pods initially look like fleshy, green pea pods, but they must completely dry out on the plant for the seeds inside to ripen fully. Over several weeks, the pods lose moisture and change color. The optimal time for harvest is when the pods have turned a brittle, pale tan or brown color.
A more reliable test for maturity than color is the tactile and auditory “rattle test.” Gently shake a few dried pods on the stalk; if the seeds are fully mature and dry, you will hear a distinct rattling sound as they move freely inside. Harvesting too early means the seeds may not be dry enough for long-term storage. Waiting until a majority of the pods on the stalk have dried ensures a maximum yield of viable seeds.
Harvesting and Extracting Radish Seeds
When most pods have turned brown and brittle, begin harvesting. Cut the entire fruiting stalks near the base using pruners, and collect them in a container or paper bag. If many pods are still slightly green, move the stalks to a sheltered, dry location, such as a garage or shed. Hang them upside down to finish air-drying for several days. The pods must be completely dry and crisp before extracting the seeds.
Threshing
Radish pods are tough, so seeds must be forcibly extracted through threshing. For a small batch, place the dried stalks into a large bucket or on a tarp and crush the pods by hand or by treading on them. The goal is to physically break apart the brittle pod walls and release the small, rounded seeds. After crushing, the resulting mixture contains seeds mixed with dry, broken plant material, called chaff.
Winnowing
Winnowing separates the heavy seeds from the light chaff. Pour the mixture slowly from one container to another in front of a gentle breeze or a fan. The heavier seeds will fall straight down into the collection container. The lighter chaff will be blown away by the air current. Repeat this process several times until the collection consists primarily of clean radish seeds.
Preparing and Storing Seeds for Viability
Before long-term storage, ensure the seeds’ moisture content is extremely low to maintain viability and prevent mold. Even if the seeds seemed dry when extracted, spreading them out on a screen or paper indoors for an additional week guarantees complete dryness. Some seed savers place thoroughly dried seeds in a glass jar and freeze them for three days. This step kills any tiny pests or insect eggs that might be present.
Once completely dry, store the seeds in an airtight container, such as a glass jar, or a paper envelope placed inside a sealed container. Paper can help absorb residual moisture, but the container must protect the seeds from humidity and pests. Label the container clearly with the radish variety and the date of harvest. Storing the seeds in a cool, dark, and dry location, such as a basement or refrigerator, helps them remain viable for up to five or six years.