Onions make it very easy for you to determine which type to plant. If you live in the northern latitudes, choose long-day varieties. Gardeners in the southern latitudes should plant the short-day type. Look for onion sets that are firm and smaller than a dime to grow big, round bulbs. Plant your onion sets in late March or early April.
Choose a sunny location in the garden in which to plant the onion.
Loosen the soil to a depth of 6 inches, crushing large clods of dirt and removing any roots, rocks and other debris.
Add a 2-inch layer of organic material, such as well-rotted manure or compost. Use the garden fork to mix this in well with the soil.
Rake the area smooth and then walk on the surface to firm it. Rake the area again, lightly, to remove any peaks or valleys.
Dig a hole in the soil deep enough so that, when planted, the tip of the onion set is exposed. Place the set in the hole and gently firm the soil around it. Plant the sets 4 inches apart.
Water only if the soil is extremely dry and crumbly.
Keep the area free of weeds. Onions have shallow roots and find it difficult to compete with weeds for nutrients and water.
Harvest your onions in late July or early August, when the tops of the plants fall over.