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picture of yellow onions in a pile picture of yellow onions in a pile


Allium cepa

onions in the ground in a field
Image by Couleur from Pixabay

Importance of Onions to Oregon

Oregon grew more than 1.5 billion pounds of onions in 2020.1 That was the third most out of any state in the country. Onions are grown by around 400 farms on close to 20,000 acres. All of the onions in 2020 were worth 118 million dollars.2 That made them the 12th most valuable crop in the state. Most of the onions are grown on the east side of Oregon in Malheur, Morrow, and Umatilla County. 

History of Onions

The exact origin of onions is not known, but there are records of them as far back as 5,000 years ago. They are thought to be one of the first crops that were cultivated. Most of the early onion records come from Egypt and parts of Asia. They can be traced through Greece and the Roman Empire and other parts of Europe, including England. Pilgrims coming to America from England in 1620 on the Mayflower brought onions with them. 

picture of the pilgrims and Native Americans at the first thanksgiving in America
Image by GPA Photo Archive on Flickr

There are onion strains that grew wild in North America. They were used by Native Americans in many ways. They were eaten in ways that we eat them today. And they were also used for medicines and dyes.3


Onion Varieties

There are different varieties of onions, with different traits and features. But we mostly see them labeled by their colors, which are red, white, and yellow.
Picture of some red onions and one of them is cut up
Image by Stephanie Albert from Pixabay


Red onion varieties are known for their dark red layers, which make them stand out in food dishes. They are very crisp and have a sharp, but tasty flavor. About 8% of US grown onions are red. They are very good raw, roasted, and grilled. 

close up picture of a bundle of white onions
Image by Patou Ricard from Pixabay


White onions make up about 5% of the onions grown in the United States. They are often used in sauces or Mexican foods, along with being roasted, grilled, or eaten raw. White onions don’t store well for as long as red and yellow onions do. 

closeup picture of a whole, yellow onion
closeup picture of green onions in a pile


Yellow onions are the most popular. 87% of the onions grown in the US are yellow. Part of that reason is because they can be used in so many ways. They are sweet and crisp and can be eaten raw, roasted, sautéed, and more. 

closeup picture of green onions in a pile
Image by Anna Armbrust from Pixabay


Red, white, and yellow onions are by far the most popular kinds of onions we see and eat. There are also other types like pearl and green onions. Pearl onions look like a white onion but are very small. Green onions are the same type of plant as the onion bulbs we eat, but are harvested when they are young before the bulb grows. We use them for the greens, not the onion bulb. 

close up picture of white, pearl onions
Image by Brett Hondow from Pixabay


picture of onions in a field curing/drying down
Image by Martin Pettit on Flickr

Life Cycle of an Onion

Onions grown for their bulbs are usually planted in the spring. Depending on the farm, they will either be planted as seed or as transplants. Sometimes onion fields are planted in the fall so that they are ready to harvest early in the summer before the spring planted onions are ready. Onion seeds are planted with a machine. Transplants are planted either by hand or by machine. 

For almost half of the time between planting and harvest, an onion’s energy is mostly spent growing leaves above ground. Then the bulb starts to grow larger. About 170 days after being planted, an onion starts to dry down and get ready to be harvested.4

Onion Harvest

Most onions are harvested in late summer or early fall. The onion leaves, called “tops” start to fall over when they are almost ready to be harvested. Before onions are harvested and removed from the field, they are lifted. This means that a machine comes through the field and cuts the roots off the bottom of the onion bulbs and loosens them from the soil. The onions stay in the field, curing for about 1-2 weeks. This gives the onion tops time to dry so that moisture doesn’t cause issues during storage.  Once the onions have cured, a machine or farm workers will harvest the onions. All of the tops are removed at that time. The onions are then taken to storage facilities where they will wait to be sent to stores and restaurants. The storage units are 35-45 degrees Fahrenheit. 
picture of onions being harvested after curing in the field for a few weeks
Image by Martin Pettitt on Flickr
Harvester Picking Up Onions

picture of a harvester machine going through a field of onions
Image by Oregon AITC on Flickr
Conveyer Belt Moving Onions Into Storage Truck After Being Picked Up

Pests and Diseases

Like all crops, onions can be damaged by insect pests and diseases. Unlike some crops, the part we eat grows under the soil. This means that insect feeding and disease infections can cause problems in onions that they might not in some crops.
picture of white onion with black spots on it
Image by S. K. Mohan on Wikimedia Commons

Black Mold

Black mold is caused by a fungus that can damage many different fruits and vegetables. Onions can get infected at the neck of the bulb where it meets the leaves. This happens close to harvest as the plant matures. It can cause areas to become covered in black spores and the onions to get soft and mushy.5

close up picture of bulb mites
Image by M. R. Bush, WA State University

Bulb Mite

Bulb mites cause onion damage by feeding on the outside of bulbs. Diseases are able to get inside damaged bulbs and cause rot and other issues. If there are very many of these insects, plants stands can be hurt and onions can grow slower or not as large. The onions can also end up rotting in storage. Bulb mites can be found in other plants with bulbs, like garlic, or in tubers.6

close up picture of insect on a flower
Image by Jean and Fred Hort


Thrips are one of the main insect pests in onions. If there are many of them, the number of onions a field grows can be cut by up to 20%. Thrips tend to eat on the young leaves of onions and they can cause bulbs to be small or misshapen. Onion thrips are vector for a disease called yellow spot virus.7

close up picture of yellow spots on an onion stalk
Image by Cynthia M. Ocamb

Yellow Spot Virus

Yellow spot virus is spread by onions thrips. The thrips spread it from plant to plant and to other fields when they feed on the onions. The virus can cause parts of leaves to dry out and die. When leaves die, there is less of a plant to photosynthesize, which can lead to the plants not growing as large as they should. The virus is usually worse around the edges of fields since it is spread by insects.8

Uses for Onions

Onions can be eaten in a variety of ways. They can be served raw, roasted, sautéed, or grilled. Onions make a good addition to soups and stews. They are a good source of fiber and vitamin C, along with a few other nutrients. 
picture of raw onion on a burger
Image by Mark Tolentino from Pixabay

picture of cooked onion on pork schnitzel
Image by Andreas Lischka from Pixabay

picture of onion rings in an orange bowl
Image by Fabricio Macedo FGMsp from Pixabay

Fun Facts About Onions!

  • Parsley can help get rid of onion breath
  • The largest onion ever known to be grown was more than 18 pounds
  • Each American eats an average of 20 pounds of onions per year
  • Sulfuric compounds are what cause onions to make us cry9


Vocabulary Terms

A plant bud that begins to grow underground. 

To grow plants by plowing, weeding, or adding fertilizer.

The process of drying out onions for storage. 

 Using sunlight to change water and carbon dioxide into food for itself.

A tiny reproductive body made up of one or more cells, produced by certain animals and plants.

Descendants of a common ancestor. 

The number of plants in a field. 

A characteristic or quality that makes a plant different from others.

To pull up and plant again in another place.

n underground stem that is short, thick, and round. 

An organism, such as an insect, that carries disease-causing fungi, viruses, bacteria, or the like.

Related Resources and Sources

        1Oregon Department of Agriculture. “Oregon Agricultural Statistics.” October 2021. https://www.oregon.gov/ODA/shared/Documents/Publications/Administration/ORAgFactsFigures.pdf. 
        2Perdue, Sonny and Hubert Hamer. “Census of Agriculture.” United States Department of Agriculture, 2017. nass.usda.gov/Publications/AgCensus/2017/Full_Report/Volume_1,_Chapter_1_US/usv1.pdf.
        3National Onion Association. “Onion History.” Accessed January 2022. https://www.onions-usa.org/all-about-onions/history-of-onions/.
        4Schwartz, Howard F. et al. “ONION Health Management and Production.” Colorado State University. 2013. https://extension.usu.edu/productionhort/vegetables/OnionHealthManagementandProduction.pdf.
        5Pacific Northwest Pest Management Handbooks. “Onion (Allium cepa)-Black Mold.” Accessed January 2022. https://pnwhandbooks.org/plantdisease/host-disease/onion-allium-cepa-black-mold.
        6———. “Onion-Bulb mite.” Accessed January 2022. https://pnwhandbooks.org/insect/vegetable/vegetable-pests/hosts-pests/onion-bulb-mite.
        7Murray, Katie, Stuart Reitz and Paul Jepson. “An Integrated Pest Management Strategic Plan for Treasure Valley Onions in Oregon and Idaho.” Oregon State University Extension Services. October 2019. https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/em9254.pdf.
        8Pacific Northwest Pest Management Handbooks. “Onion (Allium cepa)-Iris Yellow Spot.” Accessed January 2022. https://pnwhandbooks.org/plantdisease/host-disease/onion-allium-cepa-iris-yellow-spot.
        9National Onion Association. “Onion Trivia.” Accessed January 2022. https://www.onions-usa.org/all-about-onions/trivia/.