by Joyce Schillen (copyright 2004)
Variety and Zone: There are three essential facts to keep in mind about growing bulbing onions. FIRST: the bulb will be no bigger than the top. SECOND: the top completely stops growing when the bulb begins forming. So grow as big a top as you can as fast as you can. THIRD: grow a variety adapted to your zone. Change of day-length is what instructs or triggers the plant to change from growing top to making bulb while the lengths of day and night differ from North to South.
Short Day Onions: Bulb formation with these varieties is triggered during the period of increasing day-length, such as we have during spring. Because days are still short at that time of year we call these "short day" onions even though they bulb when days are getting longer.
Intermediate Day Varieties: Planted very early in spring and are adapted to day-lengths found in the intermediate Zones where the growing season is long and maximum day-lengths don't get as extreme as they do in the North.
Long Day Varieties: Bred to grow in the North. These grow tops while the days are very long and begin bulbing only after day-lengths have decreased from their maximum on June 21st to about 14-15 hours. In the North, this happens from late July through early August.
Soil Preperation: Onions demand light, loose soil and do their best in sandy loam. Amend heavier ground with compost or manure. This is usually best done the previous autumn. The important thing is to encourage them to grow tops as rapidly as possible. This means lots of fertilizer early on. Onions have coarse, small root systems. So place the fertilizer close to the plants and side-dress and/or foliar feed them. Once bulbing beings there is no point in fertilizing them anymore; the bulb's size is already determined by the size of the top.
Planting: Onion seeding are quite hardy and can withstand 20° F frost. They should be set out 4-6 weeks prior to the last expected spring frost. When your plants arrive they should appear to be quite dry. DO NOT WET THEM NOR STICK THEIR ROOTS IN WATER. Unpack them and store them in a cool, dry place until it is time to plant. They should last about 3 weeks kept this way. Do not worry that your plants seem dry. They will "shoot" new roots and new, green tops as soon as they are planted. Be sure to specify on your order when you want your plants to arrive.
Watering: Onions have small, inefficient root system and need moist soil. Keep them constant ly well watered. But when the plants approach maturity their bulbs stop enlarging and begin to form skins. When this happens, withhold further irrigation and hope it does not rain much. Ideally, the bulbs will mature in very dry soil. This helps the skins to cure and makes your bulbs keep better.
Harvest and Storage: After most of the tops have "gone down," lift the bulbs. It may help to gently loosen them with a shovel first. Allow them to lie in the sun for a day or so, then cure and store them like garlic bulbs or shallots (see the growing directions for these vegetables).
Spring Planting
