Even though onions are cheap enough to buy by the bagful, for the greatest variety, you have to grow your own—and it’s not difficult to do. Here are some onion planting, growing, and harvesting tips!
Sure, we could just buy onion sets and plant those but there is not a wide choice of varieties available as sets—mostly ‘Stuttgarter’ or ‘Ebenezer’ and often they form a thick-necked onion that wants to go to seed instead of forming nice, firm bulbs.
Which Onion is Right for You?
Determining whether to start with onion sets, seeds, or plants depends somewhat on what is available to you. Here’s a primer:
Onion sets are tiny onions that will become full-size onions in about 14 weeks. Look for small sets no bigger than three-quarters of an inch in diameter. Larger ones often produce onions with thick necks that tend to go to seed. The choice of varieties is limited; two common ones are ‘Stuttgarter’, a flavorful, semiflat, yellow onion that grows and stores well, and ‘Ebenezer’.
Onions grown from seed keep well and are less likely to go to seed. Here you also get the widest range of varieties: red, yellow, or white; round, flat, or long; mild and sweet or pungent and tangy. Onion seeds should be started indoors, as they need soil temperatures above 50°F to germinate.
Onion plants are limited to the offerings at your local gardening center and some mail-order services.
Onion seeds need to be started indoors in cold climates like mine (Zone 5). We plant 2 seeds per cell and grow them inside until the weather has warmed up enough to plant them outside. It is easier to separate two plants and transplant them than if we started the seeds in a crowded community flat and had to tease lots of plants apart before planting them outside.
Long Day or Short Day Onions?
Onions are photoperiodic, which means they are sensitive to the amount of daylight they receive. When days last 12 hours or more, leaf production stops and bulbs begin to form. Since the farther north you go the longer days are in the summer, different varieties of onions have been bred for different parts of the country. Should you plant long day or short day onions? Imagine a line running across the country from the border between North and South Carolina to San Francisco (roughly 36 degrees latitude). If you live north of that line, plant long day types; south of that line, short day onions will do best for you.
Long Day Onion Varieties
Some good long day onions are:
- ‘Walla-Walla’ or ‘Ailsa Craig’ if you want huge onions.
- ‘Red Wing’, ‘Red Florence’, or ‘Southport Red’ are good reds.
- ‘Copra’, ‘Yellow Globe’ or ‘Sweet Sandwich’ are good keepers.
Short Day Onion Varieties
A few good short day onions are:
- ‘Yellow Granex’ for sweet Vidalia-type onions.
- ‘Texas 1015-Y Supersweet’ or ‘Red Creole’ store well.
- ‘White Bermuda’ for a mild onion.
What About Day-Neutral Onion Varieties?
Day-neutral onions don’t care about day length and will produce an excellent crop in any part of the country. Some catalogs refer to them as intermediates.
Some good day-neutrals are:
- ‘Super Star’ is a mild white that produces large, sweet bulbs.
- ‘Candy’ is a yellow that stores well. It can grow to be softball-sized.
- ‘Red Stockton’ is a large, globe-shaped red that also stores well.
All onions appreciate an early start since temperature and day-length trigger bulb formation. Cool weather encourages heavy leaf growth so it is important to get your onions growing before warm weather hits. Young onion plants will not be harmed by light frost.
In the South, onions can be planted in the fall and overwintered to give them a headstart on the growing season. Since they continue to grow throughout the winter, they will be ready for harvest in May.
Onions prefer sweet fertile soil with near neutral pH and need lots of sunshine. The sulfur that gives them their bite comes from sulfur in the soil. Since they are shallow rooted plants, keep them well weeded and use mulch to keep the soil cool and moist. Onions grow best if planted where lettuce or squash grew the previous year but do poorly if they follow a cole crop.
How do you know when to harvest onions?
When the onions’ tops begin to dry out and fall over, push them all over and withhold water for about 1 week. Pull the onions and spread them out in the sun to allow the foliage to dry and the skin to toughen up, and they will keep better. If it is rainy, let them dry in a protected place such as a shed, garage, or barn.
Once cured, they can be hung in a mesh bag, spread no more than two deep in a box, or braided and hung in a cool (40° to 60°F), dry, well-ventilated area. Check periodically for sprouting or rotting onions and remove them. Do not store them in the refrigerator; it is too damp.
Sweet onions do not keep well because they have a high water content. To avoid bruising, store them so that they don’t touch each other. One way to do this is to use clean old panty hose. Slip in the onions one at a time, tying a knot between each one. Hang them in a cool, dry place.
In the Middle Ages, it was believed that onion juice could cure baldness, snakebite, and rabies. We can’t vouch for this, but we can promise that onions will add flavor to your food. No good cook should be without them!
Do you grow onions in your garden? Read more about onions in our Onion Growing Guide.
Reader Comments
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More info...?
I'd be glad for more tips on growing onions. There were a few that I was surprised that were missed. Onions do not like to be planted deep. They must be planted shallowly, and mulch kept away from them for them to grow bulbs. If you plant them too deep you just get green onions. If you start them from seed, you need to give them a "haircut" when they are about 4" high to help them produce bulbs. Mine did not do well this year - I don't think I planted early enough, and our soil is poor. But I'll keep trying and watching for tips!
garlic
do you grow garlic the same as onions and how long till harvest , can they be planted at any time of the yr.
Onions
Hello I am in Wyoming and am trying for years to grow large onions. Is it possible here? I start seeds early and plant in the ground at the proper time using long day onions and also plant sets in the ground at the same time. We have a very short growing season maybe 3 months if we are lucky. My problem is they never grow any larger than a large egg? the tops occasionally fold over but not very many fold before we freeze outside (this year 24 degrees the very beginning of Oct.) Would covering them like a cold frame help in the fall to allow them to grow longer? been trying for years now and have the same results. I grow walla walla and have tried a lot that claim to be large but to no success any help would be a blessing and Thanks for your time.
How frustrating for you! I
How frustrating for you! I have heard that the growing season in Wyoming ranges from short to very short. There are many other factors to consider too. Since soil is the key to any success in the garden, have your tested to make sure nothing critical is lacking. Onions like loose, crumbly, sandy loam with a high level of organic matter. Since onions are shallow-rooted, competition from weeds will affect their growth so be sure the beds are kept weed-free. To grow a good-sized bulb, water is important. The closer you get to harvest time, the more water is needed. Stop watering when the tops begin to fall over. Fertilize early on every 2-3 weeks with a high nitrogen fertilizer then stop fertilizing when the bulbs start to swell. Usually this happens around the time of the solstice when there is 14-16 hours of daylight. Harvest when 2/3rds of the tops have fallen over. In your area the onion season is typically from mid-April planting to mid-Sept. harvest. If your plants look like the tops still want to grow, by all means try covering them with reemay or some other form of protection from the early cold to keep them growing. Bear in mind that it is not only temperature that signals them to be done but also day length which is something you have no control over. It would not hurt to try some other varieties. I also have a short growing season and have found that generally ‘Ailsa Craig’ gives me larger onions than ‘Walla Walla’ and earlier too. Hope some of this helps!
Transplant date?
I’m sorry if I missed this in the article, I looked but didn’t notice it.. when is the best time to transplant the seedlings to the garden?
Onions are pretty cold hardy
Onions are pretty cold hardy so they can be planted early in the spring, as soon as the ground can be worked. Look at the link to the Almanac’s Onion Growing Guide for more info.
planting dates
as below Jan 26, 2017 ---seems to be a broken link, I cannot access this
When?
What is the best time to start the onion seeds indoors? I live in a 5a Zone.
planting dates
Go to the Gardening section of this Web site for the planting calendar: https://www.almanac.com/gardening/planting-calendar
I would like to know how or
I would like to know how or where to get winter onions for West Virginia planting
Hi Nancy, I have never grown
Hi Nancy, I have never grown winter onions since my winters are too cold. Success will depend on what your hardiness zone is. I know that zone 8 gardeners need to plant their winter onions in Oct/Nov and they will be harvesting them in March/April. Looks like you are too late for this winter. You can plant for this summer though. Check out your local garden center, order plants from a catalog, or start your own plants from seed.