All parts of the onion plant … If you cover the onion with a little soil it will probably go to seed NEXT year, not this year. Eat the whole green onion. Before we talk about how to harvest onion seeds, we need to say a few words about what kind of onions you can harvest onion seed. Many of the seeds or sets acquired from large seed production companies are hybrids,which means the seeds … If planted in the fall, that is what they do, go to seed. Any larger dry onions planted in the spring will usually flower. For onions… In response, it will send up a flower stalk to produce the next generation. Cut that seed leaf and take it in and eat it. If you plant very small dry onion sets in the spring, they will usually make a bulb. Onions are very hardy. It will not go to seed this year because the tops have fallen over, and so now the onion … Onions are biennial. As you likely already know, onions are a biennial crop, so exposure to cold temperatures will signal the plant that it is nearing the end of its lifecycle.