Here is our collection of all our onion seeds. Onions are a biennial vegetable grown commonly as an annual. While the seeds can be harvested in the second year. Usually they are harvested after the first year for taste. Ah, the humble onion. Harvested and grown for centuries as a staple food, the onion has layers of history in cuisines around the world. While you can plant onions from transplants or sets, growing onions from seed offers the most cultivars and disease resistance. Mountain Valley Seeds carries a myriad of different varieties, ranging from bulb to bunching types.