Who doesn't like onions? Since I started gardening many years ago, onions have always had a place in the garden, but I still envy the softball size ones in the store. Growing onions in the north can be somewhat of a challenge; a few simple guidelines might help.
Most members of the allium family -- onions, garlic, chives, leeks and shallots -- are biennials. They put on vegetative growth the first year and bloom the second year. This is especially important to remember when growing onions and garlic. There are a few perennials like the Egyptian walking onion that we like to use as green onions early in the season.
There are three ways to grow onions: from sets, from plants that are transplanted and direct seeding. There is no question which one is easiest. It's so simple to buy a bagful of sets from the garden center or grocery store and plant them 1½-2deep in rich well-drained soil with the pointy end up. Remember they started life last year from seed so are more likely to throw up a flower stalk or split especially if you select the largest sets. Select dime size sets or smaller and keep the water consistent. The disadvantage of set onions is that they do not keep as well and you have little choice in variety. If they send up a flower stalk, cut it off or pull it and use it right away, it will not get much bigger.
Direct seeding onions is the most challenging here. The season is too short unless you use a tunnel cover or want green bunching onions. We have had very good luck direct seeding HeShiKo, a bunching or green onion that is wonderful to eat raw, stir fried or in a salad. Since onions are not frost tolerant, they must be seeded after all chance of frost is gone, often a two-month window here.
More time consuming, but also more rewarding, is starting your own transplants or buying onion plants to transplant. You have far more choice of variety and can raise onions that can last until spring if you don't eat them all first. If you buy plants, be sure they are moist and actively growing. Avoid dry plants, they are dormant and will take much longer to catch up to green plants. For growing up north, choose "long-day" or day-neutral varieties. They will begin forming bulbs when the day length reaches 15-16 hours.
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Start onions inside in sterile medium 8-12 weeks before you expect to transplant them to the garden. Keep them watered, trimmed to 3-4 inches, and limit light to 12 hours per day to prevent early bulb formation. I like to use a deep flat and simply sow them in rows ¼-½ inch deep. Harden the plants off for one or two weeks outside before transplanting, and then transplant them just deep enough for the roots to "catch." Do not mound them up as it increases the possibility of stem rot.
Choose varieties depending on your taste and how long you wish to store them. Walla Walla is exceptionally sweet but does not keep. Candy is a day neutral that will reach softball size. Alisa Craig and Sweet Spanish hybrids are excellent keepers as is Copra Hybrid. Red Wing and Mars are great red onions. If you prefer pungent European flavors try Greek Salad, Rossa Di Milano, Cippolini or Red Torpedo. Have an adventure with onions this year.
Reliable information about horticulture-related topics is available at the Minnesota Extension Service web site, www.extension.umn.edu , as well as by contacting local Master Gardeners.
