Collecting onion seeds can be challenging as the seed stalk will not develop until the second year if grown from seed. Because vegetables grown from seeds taken from hybrid plants tend to be inferior to the parent plant, avoid harvesting onion seeds from hybrids, bought in seed packets will show it as being F1.
Growing onions from seeds will require about five months for the plants to mature, which is why some gardeners start their onions by planting small bulbs (called sets) or small plants.
- Watch for the seed heads to form on unharvested onion plants. This will happen after the spring growth. Seed heads are a round cluster of tiny flowers atop a tall stalk.
- Allow the seed head to mature and dry on the plant.
- Remove the dried seed head from the plant and place it immediately into a paper envelope, to prevent the seeds from dropping to the ground should the seed head break open.
- Leave for a few more months and then drop the dried seedhead into a sieve and it is then easy to separate the seeds from the dried pod.
- Make sure to label the container with the variety of seeds enclosed and include the month and year that you collected the seeds. Store the seeds in a cool dry location.