Simple steps to harvesting and preserving onions

Onions add a lot of flavor to our food, and they are easy to grow, harvest and preserve for later use.

Various onions.
Photo by Jeannie Nichols/MSU Extension.

Onions offer flavor, texture and color to the foods we eat. They can be eaten raw, cooked or pickled and are very easy to grow, harvest and preserve. There are yellow, white, green and even purple onions, producing a variety of flavors from pungent and strong to mild and sweet.

Bunching onions, such as green onions, are simply immature onions and should always be kept refrigerated. For bulb onions, Michigan State University Extension recommends storing them in a cool, dry location, ideally 35 to 55 degrees Fahrenheit with a low humidity (between 65 to 70%). These conditions should keep onions safely for one to eight months.

Sweet onions are an exception, as they have a shorter shelf life because of their lower pyruvic acid content. Therefore, they should be used within two to three weeks. A strong or pungent flavored onion is generally used for soups and stews or casseroles. For eating raw or in dishes such as stir fries, a sweet onion is often better.

When growing onions in cooler climates, MSU Extension recommends buying a long-day onion or they will not bulb. Onions grown in Michigan are planted in April to May, and they are harvested typically in August-September. Onions require lots of water for optimal growth and can be harvested at any time during their growth. Stop watering when the onion bulbs are ready to be pulled and harvested. They are at full maturity and ready for harvest when at least half of the tops of the onions start to dry out and fall over onto the soil.

After pulling them out of the ground, place the onions immediately in a garage or other dry, well-ventilated area and spread them out to dry for several days. Onions are ready to be stored when all the tops are dry and brown. To store your onions for later use, remove any loose dirt and cut off the dry tops to within one to two inches from the top of the bulb. Then, trim the roots off the bottom of the onion bulb. Be sure to leave the outer protective dry skin in place around the bulb. Make sure all the soil is removed from the outer layer of the onion so there isn’t any possibility of mold or rot beginning on the onion bulb while it is stored. Just prior to using the onion it is recommended to wash the exterior of the onion before you cut, chop or slice.

Freezing diced onions is a convenient way to preserve them as they are one of the few vegetables that do not need to be blanched.  Simply chop the onions into the desired amounts, seal, label and freeze in freezer safe containers.  These onions will be ready for use in cooked dishes. You can learn more about canning or freezing onions in the Michigan Fresh Using, Storing and Preserving Onions bulletin. Additionally, if you choose to dry them, use a food drier. It is very easy and can be done in five easy steps:

  1. Rinse the onions.
  2. Remove outer “paper shells.”
  3. Cut off tops and root ends.
  4. Slice onions 1/8 to 1/4 inch thick.
  5. Place them in the dehydrator for three to nine hours.

Onions, like all vegetables, should be brittle or crisp when thoroughly dried. Onions have components that make us cry, but they have so much potential to add flavor, nutrition, and variety to our meals that they are worth a few tears.

For more information on how to make the most out of your produce, visit MSU Extension's Michigan Fresh website for factsheets, videos, recipes and more.

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