In all three methods, the onions are planted as soon as the garden can be tilled in February through April. Good fertility, adequate moisture and cool temperatures aid development. Onions start bulb formation when the day length is of the proper duration. Different varieties of onions require different day length to initiate bulbing. High temperatures and low humidity are advantageous during bulbing and curing.
Onions are shallow-rooted and compete poorly with weeds.
Timely, shallow hoeing and cultivation are important, especially when the onions are small. Sources There are many different sources for these cultivars. Transplanting young onion plants has become a popular method of growing large, dry onions for slicing. It is the most common way to plant short-day onions. Space the plants 4 to 5 inches apart in the row to produce large-sized bulbs.