Onion seeds are sown directly or pre-germinated in trays. Onions grown from seeds are healthy and easier to store over the winter than those grown from bulbs. Onions can also be sown in late summer and overwintered under straw mulch, so you have early onions.
Spring onions are only available as seeds, so sow them directly in the vegetable garden or large pots. Spring onions or Chives are also perennials and leftovers from the vegetable garden can be put into the herb bed and used as a large chive. Flowers and seeds are fantastic in salads and marinades.