Long day onions are grown in northern areas of the U.S. where they get 14-16 hours of light. Short day varieties are grown in southern areas where by early summer the receive 12 hours of light. Onions require very fertile soil. Work manure and fertilizer into the soil before planting. Onions can be started from seeds, transplants, or sets.
Onion sets are the most popular way to plant.
Seeds must be started 12 weeks before the outdoor planting time. Onion sets should be planted in rows between 12 and 24 inches apart. The sets should be planted 3 inches apart. Onions that store the best are varieties with the most pungent flavor.