Onions, a popular cool weather vegetable, can be grown from seeds, transplants or sets. Dormant buds you can plant directly into the garden, sets quickly establish themselves and can be used to cultivate green onions and large storage onions. Onion sets, however, are rarely labeled by variety. Instead, expect to see them separated by color--white, yellow or red.
Purchase onion sets early in the season. Sets that have begun to grow in nurseries or greenhouses are more likely to flower. After flowering, onions will no longer grow.
Divide onion sets by size. Smaller onions produce the best bulbs for large onions.
Prepare the soil by tilling or turning the dirt in the early months of spring. Onions prefer loose, well- draining soil.
Plant onions with the point turned upward. The rounded end of the onion set is the bottom.
Cover the onion bulb with approximately 1½ to 2 inches of soil. The University of Minnesota Extension recommends spacing sets used for green onions close together, almost touching. For larger onions allow 3 to 4 inches between plants.
Cover the onions with soil. Onions only need about inch of moisture per week. Water if the season is dry or a full week goes by without moisture.
Harvest onions when the green tops are approximately 6 inches tall.