Growing Onions

Planting, Growing, and Harvesting Onions

By The Editors
Onions
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Onions are a cold-season fall or spring crop, easy to grow because of their hardiness. Whether you start your onions from seed, sets, or seedlings, there are some tricks of the trade that make the difference between a great crop and a disappointing one. We’ll show you how to grow onions so perfect they could make you weep!

Onions can be planted in either the spring or fall. Onion plants grow well in raised beds or raised rows at least 4 inches high. We usually plant a mix of white, yellow, and red onions.

Should I Grow Onions from Seed or from Sets?

We prefer planting onion sets over starting them from seeds, simply because the sets establish quickly and are easier to plant. Onion sets are small onion bulbs that are sold specifically for gardening. Once planted, they develop into a full-size bulb after about 3½ months.

Also, onion sets can be planted without worry of frost damage and have a higher success rate than planting from onion seeds or transplants.

Of course, starting onions from seed is certainly doable, and may even be necessary in colder regions (Zone 5 and colder). If you’d prefer to try this method, check out our tips for growing onions from seed indoors.

Planting

When to Plant Onions

  • Onions can be planted in both the spring and fall. Generally speaking, plant onion sets outdoors when the weather is cool—not cold.
    • A fall-planted crop of onions needs at least 4 to 6 weeks of warm temperatures to become established in the ground. They will remain dormant during the cool season, but be all primed and ready to grow when spring arrives.
    • In regions with a frigid winter, be sure to plants onion sets in the spring as soon as the ground can be worked—usually in March or April. Ideally, time your planting so that outdoor temperatures no longer dip below 28°F (-2°C) after the onions are in the ground.
  • Fall-planted onions are a great way to enjoy an earlier and larger bulbed harvest from next year’s garden. Plant in the warm autumn soil so that they may establish a strong root system before winter sets in. As the cold chill of winter arrives, the crop goes dormant. Then, as the temperatures and soil warm again in early spring, the onions come back to life.
  • If starting onions from seeds, start them indoors about 6 weeks before you plan to transplant them to the garden. Onion seeds need temperatures of at least 50°F (10°C) to germinate properly. 

Preparing the Planting Site

  • Growing great onions, whether in the spring or fall, all starts with soil that is well-drained, loose, and fertile. Compacted, rocky, or clay-heavy soil will affect bulb development.
    • Tip: If you live in an area with heavy clay or hard soil, add in aged compost (humus) to improve soil texture. Read more about preparing the soil.
    • Add aged manure or compost to the soil in the fall or early spring. Onion plants are heavy feeders and need constant nourishment to produce big bulbs.
  • Select a location with full sun, where your onions won’t be shaded by other plants. The more energy they can get from the sunlight, the larger their bulbs can grow.
  • At planting time, add about an inch of compost to the bottom of each row before planting. Or, dig a trench in the soil about 2 inches deep and 3 inches wide, and then fill the trench back in with about an inch of compost.
  • Practice crop rotation with onions. In other words, don’t plant them in the same location year after year, as this can encourage the spread of diseases that affect the crop. Learn more about crop rotation.

Onions in a row

How to Plant Onion Sets

  • Choose onion sets that are around ¾-inch in diameter and no bigger. Larger ones may produce stiff necks and go to seed too quickly.
  • When planting onion sets, plant them between 2 and 6 inches apart.
  • When planting larger transplants into the garden, space plants 4 to 5 inches apart in rows 12 to 18 inches apart.
  • Set the bulbs with the point end up and don’t bury them more than 1 inch under the soil. It’s important that onions aren’t planted too deep, as this can affect bulb development.
  • Find more tips for planting onions in different regions and soils.

Spacing for Onions

 

 

Care

How to Care for Onions

Think of onions as a leaf crop, not a root crop (such as beets or carrots)!

  • Fertilize every few weeks with nitrogen to get big bulbs. Cease fertilizing when the onions push the soil away and the bulbing process has started. Do not put the soil back around the onions; the bulb needs to emerge above the soil.
  • Once bulbs have started to develop, mulch with a light ½-inch layer of straw (shredded leaves work well in the fall, too). Mulch will help retain moisture, suppress weeds, and allow air circulation.
  • Generally, onion plants do not need supplemental watering if mulch is used. About one inch of water per square foot per week (including rain water) is sufficient. If you want sweeter onions, water more.
  • Onions will look healthy even if they are bone dry, so be sure to water during drought conditions. This helps to prevent onions from bolting, which is when a stressed plant speeds up its development of flowers. 

See our video demo to see how to plant and grow perfect onions! 

Pests/Diseases

  • Thrips: To control thrips—tiny insects about as fat as a sewing needle—take a dark piece of paper into the garden and knock the onion tops against it; if thrips are present, you will spot their tan-colored bodies on the paper. A couple of treatments with insecticidal soap kills them. Follow the package directions. Spray the plants twice, three days apart, and the thrips should disappear.
  • Onion Maggots: Cover your emerging onion crop with a fine mesh netting. Seal it by mounding soil around the edges. The onion maggot likes to lay its eggs at the base of plants, so the netting should prevent that. You should also keep mulch away because the insects like decaying organic matter, and make sure you completely harvest your onions as the season progresses. Onion maggots are usually a problem in very rainy periods, so these precautions may be unnecessary if you have a dry season.

Harvest/Storage

How to Harvest Onions

  • Spring-planted onions tend to be ready for harvesting by mid-summer. 
  • Pull any onions that send up flower stalks; this means that the bulbs have stopped growing. These onions will not store well, but can be used in recipes within a few days.
  • When onions start to mature, the tops (foliage) become yellow and begin to fall over. At that point, bend the tops down or even stomp on the foliage to speed the final ripening process.
  • Loosen soil around the bulbs to encourage drying.
  • Be sure to harvest mature onions by late summer, and do so in dry conditions. Onions harvested when wet do not cure well and may rot in storage. Mature onions may spoil in cool fall weather.
  • When tops are brown, pull the onions. Handle them carefully, as the slightest bruise can encourage rot. 

ONions. Photo by Rootstocks/Getty Images
Photo by Rootstocks/Getty Images

How to Store Onions

  • Clip the roots and cut the tops back to 1 or 2 inches (but leave the tops on if you are planning to braid the onions together).
  • Let the onions cure on dry ground for a few days, weather permitting, or in a protected place such as a garage or barn. 
  • Once cured, hang onions in a mesh bag or nylon stocking, layer them (up to two layers) in a box, or braid and hang them in a cool, dry, well-ventilated area. The ideal temperature range for storage is 40 to 60°F (4 to 15°C). Do not store in a refrigerator, as conditions will be too damp.
  • Check periodically for sprouting or rotting onions and remove them.
  • Don’t store onions with apples or pears, as the ethylene gas produced by the fruits will interrupt the onions’ dormancy. Onions may also spoil the flavor of these fruits (as well as potatoes).
  • A pungent onion will store longer than a sweet onion. Eat the sweet varieties first and save the more pungent onions for later.

Check out this video to learn how to harvest and store onions.

Recommended Varieties

Onions are sensitive to daylength, so varieties are generally classified into three categories: Long-day, short-day, and day-neutral. The border between long- and short-day varieties lies roughly at 36 degrees north latitude (aka, the 36th parallel)—north of this line, plant long-day varieties; south of it, plant short-day varieties. Day-neutral varieties can be grown with success anywhere!

Long-day Varieties

  • ‘Yellow Sweet Spanish’: large, round shape; yellow-white.
  • ‘First Edition’: high-yielding, stores well, flavorful, creamy-yellow
  • ‘Red Wethersfield’: flat bulbs that store well, white flesh, red-skinned
  • ‘Aisa Craig’, ‘Walla Walla’: huge bulbs
  • ‘Buffalo’, ‘Norstar’: produce crops quickly, but don’t keep very long after harvesting
  • ‘Copra’, ‘Southport Red Globe’, ‘Sweet Sandwich’, ‘Yellow Globe’: store very well
  • ‘Red Florence’: produce bulbs with an oblong shape

Short-day Varieties

  • ‘Stuttgarter’: sold in sets, early maturity with slightly flat shape, yellow
  • ‘White Bermuda’: extremely mild, with thick, flat bulbs; white
  • ‘Red Burgundy’: good table onion with mild, sweet white flesh, red-skinned
  • ‘Crystal Wax White Bermuda’: a great onion for pickling when harvested at “pearl” size
  • ‘Hybrid Yellow Granex’: sweet, Vidalia type
  • ‘Southern Belle’: ruby-color flesh and skin
  • ‘Texas 1015-Y Supersweet’: stores very well

Day-Neutral Varieties

  • ‘Candy’: golden, thick flesh; jumbo bulbs; stores well
  • ‘Red Stockton’: large, red-ringed, white-flesh bulbs
  • ‘Super Star’: large, sweet, white bulbs

Wit & Wisdom

Can You Plant a Sprouted Onion? 

Yes, you can plant a sprouted onion, though you won’t get more onions from it. You will get lots of tasty green sprouts, however! Here’s how to do it:

  1. Fill a pot with potting soil and make a hole in the middle that is about the depth and width of the onion.
  2. Place the onion in the hole and cover with soil.
  3. Water and put the pot in a sunny spot.
  4. Harvest the green sprouts as needed for cooking.

If you get a sprout with a flower, wait until the flower goes to seed. Save the seeds for planting in the spring.

Onion Cures and Home Remedies

  • In the Middle Ages, it was believed that onion juice could cure baldness, snakebite, and headaches.
  • A generation or two ago, children were treated with a poultice of mashed onions applied as a paste to cover a wound.
  • A whole onion eaten at bedtime was prescribed to break a cold by morning, and sliced onions were placed on the soles of the feet to draw out fever.
  • Early settlers made a cough syrup by steeping raw onion slices in honey overnight.
  • A raw onion rubbed on a bee sting or insect bite will relieve the pain and itching.

Onion Weather Folklore

Onion’s skin very thin,
Mild winter coming in;
Onion’s skin thick and tough,
Coming winter cold and rough.

Recipes

Cooking Notes

To make onions taste milder, soak them in milk or pour boiling water over the slices and let stand for 20 minutes. Rinse with cold water.

Chopping onions can sometimes look like a daunting task: There’s the skin, and the layers… Where to begin? Check out our tips for chopping onions in four easy steps. Onion skins actually have several health benefits, too, so don’t throw them out!

For more tips on using onions in the kitchen and cooking them correctly, click here.

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Reader Comments

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Onions rotting

Submitted by Ollie Kovaluk on July 30, 2021 - 9:11am

I have a beautiful lush garden; I plant everything according to the Farmers Almanac - thank you so much! I’m a organic gardener. Last year my onions were rotting early in the season...I thought it was because I used wood ashes to prevent worms. I planted onions sets in a different area this year. Same problem, greens start turning yellow and die...the small onion bulb is rotting. They are definitely not overwatered - I never had this problem before, some of my friends are experiencing the same thing. Are we buying infected onion sets?

onion rot in the ground

The Editors's picture

Submitted by The Editors on August 4, 2021 - 4:14pm

Sadly, this sounds like white rot pathogen. It’s probably nothing you did, certainly not knowingly. The cooperative extension tells us that it’s the fungus, Stromatina cepivorum Berk. The pathogen persists as small, dormant structures (sclerotia) in the soil. Sclerotia remain dormant in the absence of a suitable host (garlic, onion, or other Allium crops), and can survive in the soil for over 20 years. There is not much you can do that you’re not going; see here https://extension.umaine.edu/publications/2062e/ for more detail. Sorry it’s not better news.

Onion

Submitted by Diane Stead on July 6, 2021 - 6:43am

I did my onion in the fall , now they are in full bloom and very tall and the green tops are hard tuff like,
Question is the top bloom are they seeds, onion bulb , if so how what do I do now ! Thank you all in advance for your advice ! Happy gardening
Diane

Worms attacking onions

Submitted by courtney on April 9, 2021 - 10:38am

Last year I had to replant my onions 3 times because of the worms. Overnight the worms would get ahold of the green part and suck it down their holes, leaving the white part sticking straight up in the air. Do you have any suggestions other than checking onions every morning and replanting as necessary? I thought worms were good for the garden, but man replanting gets old fast when you plant 300 feet of onions!

Growing onions

Submitted by Jan on February 4, 2021 - 8:32am

Just read your article about planting onions. It is quite informative. But I have a question. In one section, you recommend mulch, but in another day that mulch harbors maggots. Please explain

Onions and potatoes

Submitted by Mrs. Gingerich on August 24, 2020 - 1:35pm

My grandpa loves to tease, and he likes to tell us you should always plant onions and Potatoes together. He says they do better that way in a dry year. When we'd ask him why, he'd say, because onions make the eyes water! Lol! They make my eyes water, but not potato eyes!!!

Growing onions

Submitted by Sharee on August 1, 2020 - 11:14am

I find that I have much better luck growing beautiful larger onions with transplants. I plant in early spring, and again about 4-6 weeks later to have young green onions longer. I plant them close together and thin them out and use as green onions until they are spaced about 5 - 6 inches apart. I then let them grow until they start to die back. I always plant the Walla Walla sweet onions (my favorite) I live on the central coast of California where the temperatures exceed 100*. I water my onions very well every day and they do great. I also love to grow my own garlic. Garlic takes longer and I usually plant in the fall and harvest them in early June.

Walking onions

Submitted by Bettina on July 24, 2020 - 9:37am

How can I grow larger walking onions?

Revive onions

Submitted by Jim Cordero on June 29, 2020 - 11:24am

I have some small onion plants that hadn’t fully developed last year. I brought them inside, hoping to dry them out and start them this year. Any tricks for those?
I believe the are Walla Walla Sweets.

onions not bulbing

Submitted by Randy Penner on May 27, 2020 - 5:15pm

The dirt needs to be removed from around the onion to allow the onion to bulb. onion grows on top of the dirt. the deeper you plant your transplants the more dirt you will need to remove. Onion maggots is my nemisus.

My onions do not bulb out.

Submitted by Carol Bowik on April 1, 2020 - 1:56pm

I planted Walla Walla onions from transplants in the fall here in CA.
This is the second year that my onions do not "bulb out". They look like leeks with a very slight swelling at the root end. I do crop rotate. They are beautiful and green and look wonderful otherwise. What am I doing wrong?

Onions

Submitted by Joan Poke on March 26, 2020 - 6:25am

I have just put my onion sets in a raised bed. Do I water and how often?
Thanks

How Much to Water Onions

The Editors's picture

Submitted by The Editors on March 27, 2020 - 9:27am

Hi Joan, Water your onions about 1 inch per week, which includes rain. 

Green Onions

Submitted by Becca on March 22, 2020 - 7:41pm

What about planting green onions, or scallions? Is it the same?

union planting

Submitted by owenga harrizon on March 18, 2020 - 12:40am

my onions are about 1month since i did transpanting and i have already weed them, so i was planning to buy an insectide so that i can spray..which one should i buy

Growing onions

Submitted by Edwin Madungwe on February 10, 2020 - 1:49am

Thank you so much for the great lesson on growing onions

onion pest

Submitted by ASIIMWE RASHID ... on July 28, 2019 - 10:40am

My onions are attacked by small insects looking like aphids and I have tried normal pesticides but they have proved ineffective during dry conditions, o please help me out if you have ever faced this challenge

Shallot sets

Submitted by Debbie Cook on May 3, 2019 - 3:39pm

I was given a 20 kg saco of red sun shalott sets and planted half, can i pickle the rest or would it not work for some reason

Onions

Submitted by John Walker on April 23, 2019 - 12:34pm

This year I bought red and white onion sets with instructions to plant 4” deep. Is this correct and what results can I expect? In the past I’ve always planted one inch deep and battled with the birds.
“

Planting Onions

The Editors's picture

Submitted by The Editors on April 23, 2019 - 3:06pm

We recommend not planting onions deeper than 1.5 inches into the ground. Deeper than that and they will struggle to do well.

onions

Submitted by Rev Ed Stephenson on February 8, 2019 - 8:06am

Where might I find "multiplying" onions... we had them when I was a kid... they "came back "every year and were wonderfully sweet...

Onions

Submitted by John Kirby on March 10, 2019 - 6:34am

I believe you are looking for Egyptian walking onions as they set a 1/4" to 3/8" seed on top of the green leaves . When left to maturity they will reseed themselves . As far as sweetness goes ,, it's partially dependent on how much you water . It is fine for them to be damp consistently but "wet" feet (soggy) is only tolerated on occasion . I get mine from the big seed stores and they can be found on e-bay as well .

TEXAS GRANO

Submitted by George Ndungu on November 3, 2018 - 11:13am

HI,I have seedlings that were left in the nursery for now more than three months is there a possibility they can groe into big bulbs i can harvest from transplanting,

Harvest onions

Submitted by Bethany Lucille Buss on August 5, 2018 - 4:49pm

I just pulled about 40% of my crop, as they’d tipped over and laid them out in a clear dirt patch. It’s 85 out there- is it okay for the onions to stay on the ground in mostly full sun? Will they burn like potatoes do?
Also, some of the ones that tipped earliest were rotting out the root end, any tips for preventing that next year.

Growing Onions

Submitted by onguru mathew on August 1, 2018 - 1:59pm

am very much thankful for the article it came at the right time, I have great passion in gardening s expecially vegetables I would like more information please

Does anyone know about or ever grown Egyptain Walking Onions?

Submitted by Maria on July 30, 2018 - 10:58am

I enjoy reading and the helpful info as I'm an avid gardener & try to be so in an environmental friendly manner. I've never seen Egyptian Walking Onions, but they look like regular ones so fat ? Any info would be appreciated. Thanks

My attempt at growing egyptian walking onions.

Submitted by Terry Joe Rogers on August 1, 2018 - 8:06pm

My grandma in Arkansas always had me go to the garden to pull a few of these onions for meals. She'd always tell me to pull off the top bulbs and spread them back over the onion patch so they can make yet more onions.
As a kid in Llano Texas I had brought back a start of grandmas onions, and before long, I had my own onion patch that we ate from.
But after we moved I lost these onions, till I found that you can order them on amazon.com. My order came in around November I think. It was a nice number of the tiny onions that Egyptian walking onions make at their tops. Before long I had my onions again. This is here in Austin Texas now where I live, and I find that they die back in the heat of the summers. But if you keep them watered, they'll come back in the fall, and really grow in the spring. This far, I've not had much luck in keeping them nice and lush in the summer however.
Anyone have any ideas as to how to keep them doing well in the summer please advise. It gets very hot and dry here in Austin Texas. Thank you. Terry J Rogers

Onions

Submitted by John Kirby on March 10, 2019 - 6:51am

Terry , I have recently moved to Hamlin , Texas . We're north of Abilene but still have hot dry summers . Last year my Egyptian walking onions struggled in the 105 degree weather we had throughout last May . There is a shade tree in one corner of my garden that is useful for veggies that don't like the heat . There was a bit of space to use and extra onion seeds as well . Remember that we have a LOT of sunshine here . The tree has heavy leaf coverage and provides a small amount of dappled sun . The onions that got the most shade have done the best . I don't know if this will work for you , but worth a try . By the way , the shade protected them from the harsh evening sun.

Growing onions

Submitted by japheth munyao on July 13, 2018 - 4:50pm

In a case where i want to grow sets instead of transplants,where do i get the sets from or how do i prepare them?

I'm growing yellow onions for

Submitted by GM on July 5, 2018 - 4:57pm

I'm growing yellow onions for the first time and am wondering if I planted one of the plants too shallow. I can see the tops and some of the actual bulb. Is there a way to remedy this or is it a lost cause?

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Growing Onions

Botanical Name Allium cepa
Plant Type Vegetable
Sun Exposure Full Sun
Soil Type Loamy
Soil pH Neutral
Bloom Time
Flower Color
Hardiness Zones
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