A well-cured onion is one of the easiest vegetables to keep. Stored properly, a good storage variety lifted in late summer is still firm and sound in April. Stored badly, the same crop turns soft, mouldy or sprouts long before Christmas. The difference is rarely luck. It comes down to three things: choosing onions that are bred to keep, curing them until the necks are completely dry, and storing them somewhere cool, dry, dark and airy. This guide explains how to store onions: which varieties last longest, how to prepare them, the conditions they need, three ways to store them, and what to do when stored onions start to rot or sprout.
- Cure first 2–3 weeks, dry and airy · until the necks rustle
- Conditions 0–5 °C · dry air · dark · frost-free
- Best keepers Firm, pungent storage onions · shallots
- Keeps Storage types until spring · mild and red types 2–3 months
Before you store: cure them properly
Almost every onion that rots in store was doomed at harvest. Wait for the tops to fall over by themselves, lift the bulbs on a dry day, and then cure them: spread them out in a single layer somewhere dry and airy, such as a greenhouse bench or an open shed, for two to three weeks. They are ready when the outer skins are papery and the neck is thin and dry enough to rustle between your fingers. Our onion growing guide covers harvesting and curing in detail.
Once cured, sort the crop before anything goes into store. Any onion with a thick or soft neck, a bruise, a split skin or a flower stem will not keep, so put it on the kitchen shelf and eat it first. Rub off loose soil but never wash onions. Trim the roots, and cut the dry tops back to 2–3 cm, unless you plan to plait them.
Which onions keep longest
Storage life is mostly a matter of variety. The best keepers are firm, pungent, long-day onions with thin necks and several layers of tight brown or golden skin. Pungent onions are also high in dry matter, and a firm, dense bulb with little free water is what keeps. Dutch storage onions such as 'Rijnsburger 5' and the F1 'Hyskin' were bred for exactly this, and keep until April or May. 'Noordhollandse Bloedrode' is one of the few red onions that also stores well, into late winter.
Mild, juicy and sweet onions do not keep as long. The Italian long reds, such as 'Rossa Lunga di Firenze' and 'Tropea Rossa Lunga', and large exhibition onions such as 'Ailsa Craig', are best eaten within two to three months. Overwintered Japanese onions last only six to eight weeks, and spring onions such as 'White Lisbon' are for eating fresh. Shallots are the champions: well-cured shallots often keep until the next crop is ready.
The conditions onions need in store
Onions want to be cool and dry. The ideal is 0–5 °C with fairly dry air and gentle ventilation, in the dark. A frost-free shed, garage or cool spare room works well. This is the opposite of what root crops need: beetroot and carrots keep in damp sand, and so do cabbages in a humid shed, as described in how to store cabbage. Damp air makes onions grow mould and roots, so never store them next to those crops, or in a cellar that stays wet.
Warmth and light both end the onion's natural rest and make it sprout. A warm kitchen is the worst place for a long-term store, though a few onions in a basket for the week ahead are fine. Plastic bags trap moisture and quickly lead to rot. Keep onions away from potatoes too, which give off moisture. Frost is less of a worry than you might think: a lightly frozen onion usually recovers if you leave it alone to thaw slowly, but bulbs that freeze hard turn soft.
How to store onions, step by step
- Cure for 2–3 weeks Single layer, dry and airy, until the necks are thin and papery.
- Sort the crop Thick necks, bruises, split skins and bolted bulbs go to the kitchen first.
- Trim and clean Rub off loose soil, trim the roots and cut the tops to 2–3 cm. Do not wash them.
- Choose a method Plaits, nets or tights, or slatted trays, but always with air around each bulb.
- Store cool, dry and dark Aim for 0–5 °C, frost-free, away from potatoes and damp root stores.
- Check every two weeks Squeeze the necks. Remove anything soft, mouldy or sprouting before it spreads.
- Eat in order of keeping Mild and red onions first, then the storage onions, and the shallots last.
Three ways to store onions
Plaits and ropes. The traditional way, and it looks good. Leave the tops on at harvest and cure them. If the dry leaves are brittle, wrap them in a damp cloth for an hour so they bend without snapping. Tie a loop of strong string, start with three onions and plait their leaves around the string, adding one onion at a time. A plait of 15–20 onions is easy to hang from a hook, and you cut onions off the bottom as you need them.
Nets or old tights. Drop an onion into the foot of a pair of tights, tie a knot above it, add the next onion, and so on. Hang the string of onions in the shed and snip off the bottom one when you need it. Every bulb gets air and none touch, so rot cannot spread. Mesh vegetable sacks work too, but do not overfill them.
Slatted trays. For a large harvest, spread onions in a single layer on wooden trays, crates or wire racks. Stack the trays with gaps between them. This makes the fortnightly check quick and easy.
Eat first
Mild, sweet or soft-necked onions that keep for weeks, not months.
- 'Rossa Lunga di Firenze', 'Tropea Rossa Lunga'
- Large 'Ailsa Craig' and overwintered Japanese onions
- Any bulb with a thick neck or a bruise
Keep until spring
Firm, pungent storage types with thin necks and tight skins.
- 'Rijnsburger 5' and 'Hyskin' F1
- Red 'Noordhollandse Bloedrode'
- Shallots, which often last until the next harvest
Why stored onions rot or sprout
Neck rot is the main cause of losses. The bulb goes soft from the top down, often with grey mould around the neck, usually some weeks after harvest. The fungus gets in at harvest through thick or damaged necks, which is why curing and sorting matter so much. Remove affected bulbs as soon as you find them. Black mould shows as a sooty powder between the outer skins; peel those layers away and use the onion soon, but throw out anything soft.
Sprouting is natural. Every onion has a rest period, and when it ends, usually in late winter, the bulb starts to grow again. Warmth and light bring it forward; cold and darkness hold it back. A sprouting onion is still good to eat, and the green shoot can be used like a spring onion. Use the sprouting ones first and check that the rest are still cool and dark.
Freezing, drying and pickling surplus onions
When stored onions start to turn, preserve what is left. Chopped onion freezes well without blanching: spread it on a tray, freeze it, then pack it into airtight bags, double-bagged to keep the smell in. Use it straight from the freezer in cooking. Thin slices can also be dried in a dehydrator or a very low oven until crisp, then kept in a jar. Small onions are ideal for pickling in spiced vinegar. Our guide to harvesting and storing your produce covers other ways to keep a glut.
Common mistakes
- Storing before the necks are dry: a green or soft neck is an open door for neck rot.
- Bending the tops over: it bruises the neck. Let them fall naturally.
- Storing mild onions for the long haul: Italian reds and big exhibition onions are for autumn eating.
- A warm or damp store: warmth makes onions sprout, and damp makes them rot.
- Plastic bags: they trap moisture. Use nets, tights or open trays.
Frequently asked questions
Should you store onions in the fridge?
Whole, dry onions are better in a cool, dry shed or cupboard. The fridge is cold but humid, which softens them over time. Cut or peeled onions belong in the fridge in a closed container; use them within a few days.
How long do homegrown onions keep?
Well-cured storage varieties keep for six to eight months at 0–5 °C, often until April or May. Mild, red and large onions keep for two to three months, and overwintered Japanese onions for six to eight weeks.
Can you store onions and potatoes together?
Not ideally. Potatoes need dark, slightly humid conditions, and their moisture makes onions rot and sprout sooner. Keep them in separate places, or at least at opposite ends of the shed.
How do you store shallots?
The same way as onions, but they keep even longer. Cure them in their clusters, separate the bulbs once they are dry, and store them in nets or trays at 0–5 °C.
A few plaits of onions in the shed, checked every couple of weeks, will keep the kitchen supplied until the first new bulbs are ready next summer. Plan next year's crop with our crop rotation plan, where onions share a bed with the root crops. Browse the Allium cepa, shallot and bulb vegetable collections, or all our seeds, and keep our growing guides to hand.
