How to Grow Onions - Part 2

A tip sheet on how to grow and care for onions.

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Onion family

Onions and their relatives are an important part of many cuisines around the world. They are considered a staple in most kitchens. There are many types and varieties to grow and all prefer looser soils, full sun and regular moisture.

Growing onions

Onions grow best in well drained and cultivated sandy, loam soil. For clay soils, work in compost to loosen compaction. Heavier soils do not allow onion bulbs to grow to their potential.

Follow your soil test recommendations for fertilizer.  Sidedress plants by lightly putting a nitrogen fertilizer alongside the plants in June.

Water to keep soil evenly moist, but not wet.

Mulch to keep soil moist and remove weed competition.

Plant onions early to get as much foliage growth as possible. Plant them after the ground has thawed in spring, when you can easily turn it with a shovel.

Onion terms

Sets are small onions grown from seed the previous year. Each set should be no more than one-half to three-quarters of an inch across, less than the diameter of a dime. Large sets frequently go to seed and cause the bulb to stop growth. The quality of the bulb is lessened. Place sets one to two inches deep in rows 12 to 18 inches apart. Sets should be separated in the row two inches apart. Cover with one inch of soil.

Onions can be started from seeds, but often produce irregular bulbs and are only good for early-maturing varieties.

Family members

Onions are one of the most common vegetables grown in home gardens. Onions are classified by:

  • Bulb shape; flat, round or globe.
  • Color; white, yellow or red.
  • Pungency; sweet or pungent.
  • Bulb’s response to day length; short, intermediate and long.

In Michigan, the most commonly grown onion is the pungent, yellow globe-type. They do best with Michigan’s cool conditions. Of the three colors of onions, yellow ones store the best.

Shallots are multiplier-type onions that divide into a clump of smaller bulbs resembling tulip bulbs. Many varieties do not set seed. Shallots have a mild, delicate onion flavor and pink outer skin when peeled. Shallots are grown from cloves, small shallot bulbs. Harvest when the tops die down in summer. Shallots can overwinter in the garden, but it is better to remove the clusters of cloves and replant a row of the small cloves in fall. Shallots can be served cooked or raw.

Leeks are grown for their thick, white stems which have a sweet, mild onion flavor. They do not form bulbs. Leeks can be served raw or cooked. They can be roasted or added to stews or soups. Start leeks indoors, four to six weeks before you want to plant, in order to harvest them in the fall. Leeks are biennial. If left until the next year, they produce flowers and seeds and the flavor becomes unpleasant. Leeks started from seed take approximately 130 days until harvest.

Bunching onions are known by a variety of names. They are also called scallions, green onions or spring onions. In England, they are referred to as Welsh onions and in the southern United States they are called “onions with blades.”

The top of the bunching onion above ground is eaten and the bulb that develops at ground level is not much thicker than the stem. Most bunching onions have white stems with green, hollow, tube-like leaves. There is also one bunching onion that has dark red to purple stems and green leaves.

These onions can be grown from transplants for a crop the same year. Plant them in a furrow four to six inches deep. As the plants grow, fill the furrow gradually or mound soil around the plants. This will increase the amount of white area on the lower portion of the plant. They are ready to harvest after very little growth. If starting from seeds, they can be started in spring or in September for an early crop next year.

Chives are grown for their leaves which have a delicate onion flavor. The leaves are cut and chopped and sprinkled on top of many dishes or mixed into dips. They are served uncooked since their delicate flavor does not withstand cooking. The bulbs are not used. Chives have round, hollow, tapering blades and grow in clumps. They produce edible purple flowers in late spring or early summer. Chives are perennials and can be easily grown in flower gardens serving double-duty as ornamental and edible plants. They can be purchased as seeds or transplants.

Garlic chives have flat leaves like garlic and leeks. The flavor is very much like garlic and the tops are harvested like regular chives. They grow taller than regular chives. Garlic chives are perennials plants with edible white flowers. Remove seedheads before they mature to prevent excessive numbers of seedlings in your garden.

Common garlic is usually grown from cloves, which are sections of the bulb. To grow larger bulbs, start the cloves the fall before and mulch during winter. Garlic will not grow if it is not watered regularly or if it has weed competition.

Elephant garlic is a different species that is grown for its large cloves and mild flavor. Growing conditions for garlic are generally the same as for onions: full sun, well drained soil, and regular moisture or irrigation.

Harvesting

Onions are finished growing when the tops fall over and dry. Leave the onions in the ground for one to two weeks for them to develop thick skin. Then dig and remove any soil clinging to the bulb, but do not wash them yet. Dry onions completely before storing. Hang them by their stems or put them in a single layer on newspaper. Do not dry in the sun. Spanish onions are very susceptible to sunburn. Remove flowers if they appear.

Originally developed by Lee Taylor and adapted by Gretchen Voyle. Reviewers Bridget Behe, Jennie Stanger and Mary Wilson. Updated 4/29/09

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