Here we are, a whole season after the first onion seeds were sown, and those tiny black specks have slowly grown into a bed of bulging brown (or red, or white) globes pushing their way out of the soil.
While onions can be harvested and eaten at any stage, the most satisfying part of growing onions (in particular, storage onions) is being able to pick a fresh onion from the pantry months after you’ve picked it from the ground.
Curing makes that possible.
What does it mean to cure onions?
Curing is a month-long process of drying down your onions to prep them for storage. Once properly cured, onions store for a very long time — through the fall and winter, and sometimes even spring under the right conditions.
But not all onions are created equally.
As a general rule of thumb, long-day varieties store longer than short-day varieties (the “long” in long day refers to the onion needing 14 to 16 hours of sun to develop properly), and pungent onions store longer than mild onions.
Mild onions are generally large and juicy with thick rings and papery skins that peel easily. They’re sweet enough to eat raw but they really shine as onion rings and bloomin’ onions.
Unfortunately, most mild onions don’t last more than two to three months, even when cured and stored under optimal conditions. If your crop includes mild onions, you’ll want to eat those first.
Pungent onions, on the other hand, can keep as long as six months or even up to a year. They’re usually smaller in size with thinner rings and tighter skins, and are best known for making you cry when you cut them.
The sulfurous compounds that sting your eyes are the same ones that inhibit rot, so the more pungent the onion is, the longer it will store.
Which onions store the longest?
When it comes to onions, we just have to accept that long-storing onions cannot be grown in the south.
Northern climates, however, have their pick of long-day storage onions that are bred for winter storage. They include white, yellow, and red globe onions with mild to moderate pungency.
Short-day and intermediate types are mostly sweet onions that store for one to three months on average.
The exceptions are Red Creole, a short-day red globe that keeps exceptionally well, and Texas Legend, a short-day yellow globe that can sometimes last up to four months.
In fact, Red Creole was my favorite onion to grow when I lived in Southern California because I could count on it to last through Christmas!
|Cultivar||Shelf Life in Storage|
|Red Wethersfield||12+ months|
|Copra||10 to 12 months|
|Stuttgarter||10 to 12 months|
|Redwing||8 to 10 months|
|Red Zeppelin||6 to 8 months|
|Red Creole (short day)||6 to 7 months|
|Blush||5 to 6 months|
|Highlander||4 to 5 months|
|Yellow Spanish||4 months|
|Red River||3 to 5 months|
|Texas Legend (short day)||3 to 4 months|
7 secrets to harvesting, curing, and storing onions from the garden
Secret #1: Wait for half the plants to fall over before you start harvesting.
When your onions are vigorously growing through the longer days of spring and summer, their stems are lush and happy and green. You might even have a few onion flowers topping those stems.
When the bulbs finish developing in mid to late summer, you’ll notice the lowest leaves start to yellow and wither. Shortly after, the stems will flop over at the neck. It starts with one or two plants, and then the rest, until it looks like your whole crop is dying.
Fear not. The leaves are key in knowing when to harvest!
Wait for one-half to three-quarters of your crop to flop, then bend over the stems of any remaining upright plants. You can simply bend them above the bulb with your hands; this is a signal for the plants to enter dormancy.
If some of your onions sent up flower stalks, you can just leave them be. The leaves around the flower stalk will still wither naturally when the onion is ready for harvest, so you don’t have to bend over the stalk. I don’t recommend cutting it off, because it could introduce bacteria into the onion during the curing process.
Secret #2: Stop watering your onion crop before harvest.
When you notice the leaves on the first few plants start to fall over, stop watering and leave the onions in the ground for 7 to 14 days (depending on how dry or humid your climate is) to allow them to finish maturing. Withholding water at this stage helps keep the onions from rotting.
The same holds true for rain — if most of your onions are fully grown, harvest them all before a big rainstorm is expected because moisture spells trouble for mature onions.
Secret #3: Dry out the roots immediately after harvest.
On a dry, sunny day, carefully pull each onion out by the bulb, or dig around the plant to lift the bulb from the soil.
Grabbing the weakened stem could cause it to pull off entirely, so make sure the stem stays intact to reduce the likelihood of rot.
Lay the onions out on the ground or in another open, sunny area for a day or two to dry out the roots.
Secret #4: Cure your onions so they keep through winter.
After a nice day of getting some sun, move the onions into a sheltered, shady spot (under a tree, on a covered porch, or in a well-ventilated garage, for example) and spread them out one by one.
You don’t need to clean off the onions yet. Just set them out to dry, dirt and all, until the stems turn brown and brittle. This rest period allows the onions to go deeper into dormancy so that they’re less susceptible to disease.
If you have absolutely no shade around your house, you can lay them in the sun but covered with a thin cotton sheet to prevent sunburn. (Never use plastic, canvas, or other thick, non-breathable materials, which could stifle them.)
If you often get rain in the summer, you can cure your onions in a garage or basement, but turn them over a couple times a week to ensure even drying. While they’re curing, onions like it warm (75°F to 80°F) but breezy.
The most important part of curing is giving them enough shade and having plenty of air circulation around the bulbs.
Because of this, it’s best to lay them out without crowding them, rather than heaping all your onions into a basket.
This last step in the curing process takes two to three weeks (and sometimes up to four weeks, if your summers are very humid).
You want your onions dry, dry, dry. The roots will become stiff and wiry, and the papery outer skins will dry out and constrict around the bulbs.
Secret #5: Trim the onions so you can see which ones to use up first.
Once the onion tops and roots have fully dried, you can tidy ’em up by trimming the roots and cutting off the stems with garden scissors. A couple layers of the outside skin will usually flake off with the stems, leaving you with a clean, smooth onion.
If you had a few onions with flower stalks growing through the bulbs, use those up first. The flower stalks retain a lot of moisture (even after curing) and will cause the onions to decay quicker in storage. They’re perfectly fine to eat and usually keep for a month or so.
Onions with blemishes or bruises should also be used up first, as well as onions whose skins came off completely.
Secret #6: Store onions in a dry, dark, and airy space for maximum longevity.
Onions store best in a cool and dry, dark and airy space, inside brown paper bags, nylon mesh bags, wire or wicker baskets, milk crates, or burlap sacks.
The ideal temperature for storage is 40°F to 50°F, but should never exceed 70°F if you want your onions to last.
Keep in mind that even after curing, onions are still very much alive and need cool, dry conditions to stay dormant. Any change in temperature or humidity can cause them to break dormancy and sprout again.
You should check your onions every few weeks for green shoots that might emerge in storage. I once let my onions linger in a warm room for a couple of months, and came back to alien-like green tentacles taking over my shelf.
(The onions were still good to eat, though — you’ll know when onions go bad, as the flesh will be moldy or turn soft and mushy. At that point, they can’t be saved.)
Secret #7: Save tiny onions to plant in spring.
If you happen to have some teeny tiny onions (I usually get a few that never got around to growing, but are too small to be used like shallots), cure them and save them for next year — you’ve just grown your very own “set” of onions!
Replant the baby onions in spring, where they’ll mature into full-sized bulbs in much less time… and you’ll have a brand-new harvest even sooner!
Frequently asked questions about harvesting, curing, and storing onions
Do you need to cure onions?
No. Onions are edible right out of the ground and can be eaten at any stage of growth. You only need to cure onions that you want to store.
Also, gardeners in warm climates who grow short-day onions may not want to go through the entire process of curing. If the onion’s only going to last a month or so, it can simply be dried (in the shade) for a few days after harvest, trimmed, and stored in the pantry for use over the next several weeks.
How do you know when shallots are ready for harvest?
Shallots mature in about 90 days and are ready to be picked in mid to late summer when their leaves start to turn brown and fall over.
Just as you do with globe onions, watch for the tops to flop, then stop watering for several days. When at least half the crop has withered, pull the shallots from the ground.
How do you cure and store shallots?
Shallots are cured and stored the same way globe onions are. Because of their smaller size, however, they cure in half the time (just one to two weeks).
Can you plant a sprouted onion?
Yes! Sprouted onions grow well in containers indoors, where you’ll have the best chance of that sprouted onion turning into a new bulb.
When an onion starts sprouting, it’s already started dividing itself. Depending on how long you’ve let your onion go, it may have just one new section, or perhaps two or three sections that look like new stems. You can plant these newly divided, sprouted sections individually, keeping the roots and sprouts intact. The sprouted section should eventually develop into a full bulb.
If it’s the wrong time of year for planting onions, you can still plant a sprouted onion in the garden for its leaves, which are edible.
If you want a fun “houseplant,” you can also regrow green onions in water.
Are onion sprouts poisonous?
Not at all. Onion sprouts (the green shoots that emerge from the bulb) are 100 percent edible, but the flavor varies from pleasantly onion-y to slightly bitter.
In my experience (after multiple taste tests), I prefer when they’re tall, tender, and leafy (like what you find on spring onions) than when they’re newly sprouted (like what you see on an older onion that’s broken dormancy).
There are many other unusual parts of vegetables you grow that are edible as well.
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Onion Harvest and Storage Sources
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This post updated from an article that originally appeared on July 12, 2012.