For flavored bulbs in a hurry, start with onion plants. You'll harvest onion bulbs just 3 1/2 months after planting. 'Long-day onions', better suited to the North, need 13+ hours of daylight for best development, while 'short-day varieties' need less and thrive in regions with a mild winter climate.
For the earliest green onions, plant sets as soon as the ground can be worked. One quart plants 50 feet. Plant 1-2 inches deep and 3-4 inches apart. Onions are ready to harvest when ¾ of the top has fallen over. After digging, leave bulbs in the garden to cure for a few days until roots are brittle. Spread out on newpaper in a dry, dark room for 2-3 weeks. Remove dirt and papery skin. Cut tops 1½ inches above the bulb. Store bulbs in mesh bags in a cool, airy room. Use those with thick necks first as they are likely to be the first to spoil.