How to Store Onions So They Stay Firm for Months

You buy a 2 kg bag of onions because it is cheaper, and three weeks later the bottom half has gone soft, sprouted green shoots or grown a grey fuzz that smells terrible. Onions are one of the longest keeping vegetables in the kitchen, so when they spoil early, the problem is almost always where and how they were kept. Learning how to store onions properly means a single bag can last two to three months instead of two to three weeks.

Below are the rules for whole onions, cut onions, cooked onions and the different types, with the times you can expect from each method.

How to store onions whole and uncut

Dry, papery skinned onions, which covers most yellow, brown, white and red onions, want four things: cool temperatures, dry air, airflow and distance from moisture. Ideal conditions are about 4 to 10C with low humidity. Few kitchens offer that, but you can get close.

Take them out of the plastic bag. Supermarket plastic traps the moisture onions release and is the fastest route to mould. A mesh bag or open basket is better.
Pick the coolest dry spot you have. A pantry on an outside wall, a cool hallway cupboard, an unheated utility room or a garage that does not freeze all work. Avoid the cupboard above the kettle or beside the oven.
Give them air. Spread onions in a single or double layer in a wire basket, crate or slatted box. Piled deep, the bottom ones sweat.
Check weekly. Squeeze each onion lightly at the neck. Soft necks spoil first, so use those onions this week.

Good storage starts at the shop. Choose onions that feel heavy for their size, with tight, dry, papery skins and no smell. Skip any with a soft or damp neck, dark patches or green tips already showing, because those will not keep however carefully you store them.

Kept this way, firm storage onions last one to two months in a normal kitchen and three months or more in a cool garage or cellar.

The old trick of storing onions in a pair of clean tights, knotting between each one, still works. Hang the string from a hook and snip off the bottom onion as you need it. Every onion gets its own airflow, and it costs nothing.

Keep onions away from potatoes

Onions and potatoes both like cool, dark places, so they often end up in the same basket. Separate them by at least a shelf or a metre of space. Potatoes release moisture, which softens onion skins, and onions give off gases that speed up sprouting in potatoes. Stored side by side, both spoil faster.

The same applies to anything damp. Keep onions away from the sink, the bread bin and any fruit bowl with bananas and apples, which release ethylene gas that encourages sprouting.

Storing cut, sliced and cooked onions

Once an onion is cut, the rules flip. The protective skin is gone, so it needs the fridge.

Half an onion: Leave the skin on the uncut half, wrap the cut face tightly in cling film or put it cut side down in a small airtight tub. It keeps 7 to 10 days at 5C or below.
Chopped or sliced raw onion: Store in a sealed glass jar or airtight container. Use within 5 to 7 days. Glass holds the smell better than most plastic.
Cooked onions: Cool within two hours, refrigerate in a sealed container and use within 3 to 4 days.
Freezing: Chop, spread on a tray for an hour, then bag. Frozen onion keeps 6 to 8 months and goes straight into soups, stews and sauces from frozen. The texture turns soft, so it is not good for salads.

Caramelised onions freeze especially well. Cook a big batch, portion into an ice cube tray, and you have a flavour base ready for months.

Sweet onions, spring onions and shallots

Not every onion behaves like a brown storage onion. Sweet varieties such as Vidalia and other mild salad onions have more water and sugar and thinner skins. They last only a few weeks at room temperature. Wrap each one in a paper towel and keep them in the fridge crisper drawer, where they hold for up to a month.

Spring onions and leeks are leafy and need moisture. Trim the roots slightly, stand them in a glass with 2 to 3 cm of water in the fridge, or wrap in a damp paper towel inside a bag. Expect one to two weeks. If you already store fresh herbs this way, the method is the same; our guide to storing fresh herbs so they last two weeks explains the jar setup.

Shallots and garlic follow the whole onion rules: cool, dry, airy and out of plastic. Shallots often last even longer than onions, up to three months.

Why "cool and dark" is not the whole answer

Almost every storage guide repeats the line "store onions in a cool, dark place". It is not wrong, but it puts the emphasis on the wrong thing. Darkness matters least of the four conditions. Moisture and airflow matter most.

A closed, dark cupboard under the sink is cool and dark, and it is one of the worst places for onions because the pipes raise humidity and there is no air movement. An open wire rack in a cool, dim corner of the kitchen beats it easily, even with some daylight. Light can encourage a little greening, but trapped damp causes the soft rot and mould that actually ruin a bag. If you have to choose, pick dry and ventilated over dark.

How to tell if an onion has gone bad

Most problems are easy to spot:

Green sprouts: Still safe. Cut the shoot out and use the onion soon, as it will be softer and slightly bitter.
Soft spots: Cut away small soft areas with a margin. If the onion is soft throughout or brown inside, discard it.
Black powder under the skin: This is a common mould. Peel off the affected layers; if it reaches the inner layers, throw it out.
Slimy texture or sour smell: Bin it, and check the neighbours, because rot spreads.

For more ways to cut kitchen waste, the full food storage and know-how section covers everything from bread to eggs.

Frequently asked questions

Should onions be stored in the fridge?

Whole, dry skinned onions should not go in the fridge, because the humidity softens them and they absorb other smells. Cut onions, cooked onions and sweet onion varieties do belong in the fridge. Keep them sealed so the smell does not spread.

How long do onions last at room temperature?

Whole storage onions last about two to four weeks on a warm kitchen counter. In a cool, dry, ventilated spot around 10C, they can last two months or more. Sweet onions last only one to two weeks unrefrigerated.

Can you store onions and garlic together?

Yes. Onions and garlic like the same cool, dry, airy conditions and do not harm each other. A shared mesh basket or slatted crate works well. Just keep both away from potatoes.