Onions are a biennial crop which means in the first year you could grow several varieties if you so wished and then choose one variety that you would like to collect seed from and allow to flower the following spring.

In the first year one needs to choose around eighteen healthy looking plants to maintain a good genetic diversity. Remove any that look unhealthy, odd shape or are likely to bolt. Late summer you will need to lift and dry the bulbs. Store them away in a frost free, dry airy place either in trays or netted bags.

The following spring, at the normal time you would be planting onion sets replant your stored onion plants discarding any that look unhealthy at 30cm spacing in blocks or rows. These will start to grow vigorously and like leeks produce long slender flower stalks . At this stage they will need staking and tied to prevent the wind from breaking the long stems. The flower head on each plant contains hundreds of tiny flowers. As the flower and plant begins to dry so the seeds form. The seeds are enclosed in tiny pods that can shatter quite easily. As soon as the pods start to dry and the seeds are mature they will need to be harvested. To avoid losing any seeds, the seed heads can be bent over and placed in a sack by cutting its stalk. The seed heads need to be placed on shelving in a protected area, away from direct sunlight to complete drying.

The seed does fall quite freely from the seed pod once the pods are dry. Removal seed techniques for the remaining seed apart from a commercial seed thresher can be jumping up and down on the seed heads or rubbing the seed heads together. Using wire mesh screens by rubbing the seed pods over the screens to extract the seed. Also, any remaining seed pods and debris can be extracted to leave just the seed through winnowing in a light wind. More information on seed drying can be found under the section ‘Seed Cleaning and Drying’ on our website.