How to Store Onions for Winter in the UK – Best Storage Methods to Stop Sprouting and Rotting

There’s something incredibly satisfying about harvesting a fantastic crop of homegrown onions from your allotment. After months of preparing the soil, planting sets, watering and looking after your plants, you finally have a collection of beautiful onions ready for the kitchen.

But once you’ve harvested them, there’s another important job to think about: how to store onions for winter in the UK.

If you get your storage conditions right, suitable onion varieties can last for several months, potentially providing homegrown onions throughout winter and into the following spring.

However, if onions aren’t dried correctly or they’re stored somewhere too damp or warm, they can quickly begin sprouting, softening or rotting.

Here at Gardening with Ben, I’ve been growing vegetables on the allotment for many years, and one thing I’ve learned is that successfully storing your harvest is just as important as growing it.

In this complete guide, I’ll explain how to harvest onions for storage, how to dry and cure them, which storage methods work best in British conditions and how to stop your onions from sprouting and rotting.

Can You Store Homegrown Onions All Winter?

Yes! Many homegrown onion varieties can be stored throughout winter, provided they’re properly matured, cured and kept in suitable conditions.

However, not every onion stores equally well.

Some varieties are intended primarily for fresh eating, while others have been developed for reliable long-term storage.

In general, spring-planted onions and certain seed-grown varieties tend to have better long-term storage potential than many autumn-planted varieties.

The length of time onions remain usable depends on several factors:

• The onion variety.
• How mature the bulbs were at harvest.
• Whether the onions were damaged.
• How thoroughly they were cured.
• Storage temperature.
• Humidity.
• Air circulation.
• How regularly the stored onions are checked.

With the correct conditions, suitable storage onions may remain in good condition for several months.

1. Harvest Your Onions at the Right Time

Successful winter storage begins before the onions are even lifted from the ground.

If onions are harvested too early, their necks and protective outer skins may not have matured sufficiently.

This can make long-term storage more difficult.

On the other hand, leaving mature onions in wet soil for too long can increase the likelihood of deterioration.

Signs Onions Are Ready to Harvest

Look for:

• Green leaves beginning to turn yellow.
• Foliage naturally falling over.
• Onion necks becoming softer.
• Bulbs reaching their mature size.
• Outer skins beginning to dry.

Autumn-planted onion sets are commonly harvested in June and July.

Spring-planted onions are generally ready between July and September, although later varieties may continue into October.

Gardening with Ben tip: Never force the leaves down to make your onions mature. Allow them to fall over naturally, then harvest when the crop is ready.

2. Lift Your Onions Carefully

When harvesting onions for winter storage, it’s important to avoid damaging the bulbs.

Even small cuts and bruises can provide opportunities for decay to develop later.

Choose a reasonably dry day if possible.

Use a garden fork to gently loosen the soil around the bulbs.

Take care not to push the fork into the onions themselves.

Lift the bulbs carefully and remove loose soil by hand.

Don’t knock onions against each other to clean them.

Once harvested, separate any bulbs that have been cut, bruised or damaged.

These onions should be used sooner rather than put into long-term storage.

3. How to Dry and Cure Onions Before Storage

Curing is one of the most important stages of storing homegrown onions.

The process allows the outer skins, necks and roots to dry thoroughly.

Proper curing helps prepare onions for storage by reducing moisture around vulnerable parts of the bulb.

If onions are placed into storage while their necks are still damp, they may deteriorate much more quickly.

How Long Does It Take to Cure Onions?

Under suitable conditions, curing commonly takes approximately two weeks.

However, cool or humid British weather may mean your onions need longer.

Rather than relying entirely on the number of days, examine the bulbs carefully.

Properly cured onions should have dry, papery skins and thoroughly dried necks.

4. Drying Onions Outside

If the weather is warm and settled, you can dry your onions outside.

Spread them across a mesh rack or other suitable surface that allows air to circulate underneath.

Avoid leaving them in large piles.

A single layer is ideal.

The Royal Horticultural Society recommends allowing onions to dry in sunshine when conditions are suitable.

However, during periods of intense heat, avoid allowing exposed bulbs to become excessively hot.

If rain is forecast, move the onions under shelter.

Advantages of Outdoor Drying

• Good natural airflow.
• Sunshine can help remove surface moisture.
• Plenty of space for larger harvests.
• Minimal equipment required.

The main disadvantage is the unpredictability of British weather.

5. Drying Onions in a Greenhouse

A greenhouse can be useful for curing onions, particularly when summer weather becomes unsettled.

Place your onions on staging, mesh racks or suitable shelves.

Leave enough space between bulbs for air to circulate.

Keep the greenhouse well ventilated.

Avoid allowing the temperature to become excessively high or the air to remain humid.

If necessary, move the onions into a more sheltered position where strong sunshine won’t overheat them.

A greenhouse may be useful for curing, but it generally isn’t the best place for keeping onions throughout winter because temperatures and humidity can fluctuate significantly.

6. Drying Onions in a Shed

A dry, well-ventilated shed is another practical option.

This is particularly useful if you don’t have a greenhouse.

Arrange onions in a single layer on slatted trays, racks or shelving.

Ensure plenty of air can circulate around the crop.

Don’t put freshly lifted, damp onions into sealed containers.

A shed that suffers from condensation or persistent dampness is unsuitable until those problems are resolved.

Once the onions have cured, they can be moved to their winter storage location.

How Do You Know When Onions Are Properly Cured?

Before storing onions, check the following:

1. Outer skins: They should feel dry and papery.
2. Necks: They should be thoroughly dry rather than green or moist.
3. Roots: They should have dried and shrivelled.
4. Bulbs: They should feel firm and healthy.
5. Smell: There should be no unpleasant odour suggesting rot.
6. Damage: Avoid storing bruised, mouldy or deteriorating onions.

If some onions still have thick, damp necks, separate them from the good storage bulbs.

These are better used sooner.

7. Best Places to Store Onions During Winter

Once your onions have dried properly, the next step is choosing somewhere suitable for winter storage.

The ideal location is cool, dry, frost-free and well ventilated.

Stable conditions are important.

Repeated temperature fluctuations can encourage condensation and deterioration.

Can You Store Onions in a Shed?

Yes, provided the shed stays reasonably dry, cool and frost-free.

A well-ventilated shed can make a useful storage location.

However, an uninsulated shed may experience freezing temperatures during winter.

If the bulbs are likely to freeze, move them somewhere more suitable.

Can You Store Onions in a Garage?

A garage can work well if it’s dry, ventilated and doesn’t become excessively warm or cold.

Keep onions away from heaters, damp walls and areas where condensation develops.

Check temperatures during particularly cold weather.

Can You Store Onions in a Pantry?

A cool pantry is another excellent option.

It can be particularly convenient because the onions remain close to the kitchen.

Choose a ventilated shelf or suitable storage container rather than a sealed cupboard with poor airflow.

Can You Store Onions in a Greenhouse Over Winter?

A greenhouse usually isn’t the best winter storage location.

Temperatures can fall below freezing at night and rise considerably on sunny days.

Condensation can also become a problem.

Unless you can maintain suitable stable conditions, use a cool shed, garage or pantry instead.

8. What Temperature Is Best for Storing Onions?

For long-term storage of properly cured onions, cool conditions just above freezing are generally ideal.

Around 2–4°C is a useful target where suitable storage facilities are available.

In an ordinary home or shed, you may not be able to maintain this temperature.

That’s fine, but warmer conditions may shorten storage life.

The most important thing is avoiding excessive warmth, freezing temperatures and large fluctuations.

Good ventilation and low moisture levels are equally important.

9. Best Methods for Storing Homegrown Onions

There are several ways to store onions successfully.

The best method depends on how many onions you’ve harvested and the space available.

Method 1: Mesh Bags

Mesh bags are one of the simplest and most effective options.

The open material allows air to move around the onions.

Hang the bags somewhere cool, dry and ventilated.

Avoid overfilling them.

Check the onions regularly and remove any bulbs beginning to deteriorate.

Method 2: Slatted Wooden Crates

Wooden crates are useful if you have a large allotment harvest.

Choose crates with gaps that allow good airflow.

Arrange onions in shallow layers rather than piling them deeply.

If possible, use a single layer for easier inspection.

Method 3: Slatted Trays or Mesh Shelves

Trays and mesh racks are particularly useful for gardeners who want to inspect their onions regularly.

Lay the bulbs out with a little space between them.

This allows you to see any signs of mould, softness or sprouting.

Method 4: Onion Plaits

Plaiting onions is a traditional storage technique.

It also looks attractive in a suitable pantry or storage shed.

Leave the dry foliage attached when curing.

Once the onions are suitably dry, carefully braid their tops together.

Hang the plait somewhere cool and well ventilated.

Use sound, healthy bulbs and avoid overcrowding the plait.

Method 5: Ventilated Baskets

Open baskets can work for smaller onion harvests.

Choose one that allows air to circulate.

Don’t place the basket in a warm, damp or poorly ventilated location.

Inspect the contents regularly.

Which Onion Storage Method Is Best?

Method	Main advantage	Best for
Mesh bags	Excellent ventilation	Small to medium harvests
Wooden crates	Practical and stackable	Larger allotment harvests
Slatted trays	Easy to inspect individual bulbs	Long-term storage
Onion plaits	Saves shelf space	Traditional hanging storage
Open baskets	Convenient and inexpensive	Smaller quantities
Sealed plastic bags	Trap moisture	Not recommended

For a substantial allotment harvest, I particularly like the practicality of slatted trays or mesh storage because you can check the bulbs easily.

10. How to Stop Stored Onions Sprouting

One of the most common problems during winter is onions beginning to grow green shoots.

Sprouting happens when a bulb starts growing again after its dormant period.

Several factors can encourage this, including unsuitable temperatures, moisture and the natural characteristics of the onion variety.

How to Reduce Sprouting

• Choose varieties with good storage qualities.
• Cure onions thoroughly.
• Keep storage temperatures cool and stable.
• Avoid damp storage locations.
• Protect bulbs from freezing.
• Inspect stored onions regularly.
• Use varieties with shorter storage lives first.

The RHS also recommends keeping stored onions in a light, cool, dry and well-ventilated location rather than leaving them in complete darkness.

You don’t need intense direct sunlight, but a suitable airy location with some light can be useful.

Can You Eat Sprouting Onions?

Yes, an onion that has begun sprouting can often still be eaten.

If the bulb remains firm and shows no signs of mould or rot, it can usually be used in cooking.

Remove the sprout if you prefer.

However, sprouting onions generally won’t keep as long as dormant bulbs, so use them promptly.

11. How to Stop Stored Onions Rotting

Rotting can be caused by disease, damage, excessive moisture or unsuitable storage conditions.

Sometimes a bulb looks healthy at harvest but later begins deteriorating.

This is why regular inspection is important.

Preventing Onion Rot

Make sure onions are fully cured before storage.

Only store firm, healthy bulbs.

Keep them well ventilated.

Avoid storing them in damp locations.

Don’t allow onions to freeze.

Remove any deteriorating bulbs promptly.

If one onion begins rotting, inspect neighbouring bulbs carefully.

Discard onions showing mould, watery breakdown or unpleasant smells.

12. Should You Remove Onion Leaves Before Storage?

Once your onions have cured and their foliage is completely dry, you can trim the leaves if desired.

Leave a short, dry neck above the bulb.

Avoid cutting directly into the bulb.

If you’re planning to make onion plaits, leave the foliage attached.

Don’t remove green leaves immediately after harvesting onions intended for long-term storage, because the necks need to dry thoroughly.

13. Should You Wash Onions Before Storing Them?

No.

Homegrown onions intended for long-term storage generally shouldn’t be washed.

Adding water to the skins and necks introduces unnecessary moisture.

Instead, allow soil to dry and gently remove loose dirt.

Avoid scrubbing or damaging the protective outer layers.

Wash onions when you’re ready to prepare them for cooking if necessary.

14. Can You Store Red and White Onions Together?

Yes, provided the bulbs are properly cured, healthy and suitable for storage.

However, different varieties may have different keeping qualities.

It’s useful to label your harvest so you know which onions to use first.

Some red and sweet onion varieties may not store as long as firm yellow storage onions.

Always check the expected storage qualities of your chosen varieties.

15. Which Onion Varieties Store Best in the UK?

If you want homegrown onions throughout winter, choosing suitable varieties makes a considerable difference.

Some popular UK storage varieties include:

Sturon: A reliable yellow onion known for good keeping qualities.

Centurion: A dependable variety with good storage potential.

Red Baron: A popular red onion that stores well under suitable conditions.

Rumba: A yellow-skinned variety noted for useful storage performance.

Hercules: A vigorous onion with good resistance to bolting.

The expected keeping period varies depending on the variety and conditions.

For the longest storage, look for descriptions such as ‘good keeper’ or ‘excellent storage quality’ when choosing onion sets and seeds.

16. How Long Can You Store Onions?

Storage life varies considerably.

Onion type	General storage potential
Many autumn-planted onions	Summer into autumn or early winter
Spring-planted storage varieties	Several months, potentially into spring
Sweet or mild varieties	Often shorter storage periods
Bolted onions	Best used promptly
Bruised or damaged onions	Not suitable for long-term storage
Properly cured, healthy storage onions	Best chance of lasting through winter

These are general expectations, not guarantees.

Some varieties perform better than others, and storage conditions can make a substantial difference.

17. Should You Store Onions and Potatoes Together?

It’s generally better to keep onions and potatoes in separate storage areas.

Potatoes and onions have different preferred storage conditions.

Potatoes are normally stored in darkness to prevent greening, while the RHS recommends light, airy storage for onions.

Keeping large quantities together may also create less suitable moisture conditions.

Separate storage makes it easier to provide each crop with what it needs.

18. Can You Freeze Homegrown Onions?

Yes.

Freezing is a useful option if you have more onions than you can store.

It’s particularly handy for sound onions that are unlikely to keep for months.

Peel the onions and chop them into suitable pieces.

Place them in freezer-safe containers or bags, label them and freeze promptly.

Frozen onions generally become softer after thawing, so they’re best used in cooked dishes such as:

• Soups.
• Stews.
• Curries.
• Pasta sauces.
• Casseroles.
• Onion gravy.

Use frozen onions according to recognised home-freezing guidance and avoid freezing bulbs that are already rotten or mouldy.

19. Common Onion Storage Mistakes

There are several mistakes worth avoiding if you want your harvest to last.

Storing Onions Before They’re Dry

Damp necks and skins increase the risk of deterioration.

Using Sealed Plastic Bags

Plastic bags without ventilation trap moisture and can encourage mould.

Keeping Onions Somewhere Warm

Excessive warmth can shorten storage life and encourage sprouting.

Allowing Onions to Freeze

Freezing can damage bulb tissues and lead to deterioration after thawing.

Storing Damaged Bulbs

Bruised and cut onions are more likely to rot.

Forgetting to Inspect the Harvest

Check stored onions regularly so you can remove deteriorating bulbs.

Mixing All Varieties Without Labels

Different varieties have different keeping qualities.

Knowing what you’ve stored helps you decide which onions to use first.

Monthly Onion Storage Checklist

Once your onions are cured and stored, regular checks can help reduce losses.

Month	Storage jobs
September	Cure and sort the harvest
October	Check airflow and remove damaged bulbs
November	Monitor moisture and storage conditions
December	Protect onions from freezing temperatures
January	Inspect for sprouting and soft bulbs
February	Use onions showing early signs of growth
March	Check remaining storage onions frequently
April	Use or preserve remaining sound bulbs

Your storage season may begin earlier or later depending on when you harvested your crop.

Frequently Asked Questions About Storing Onions

What is the best way to store onions for winter in the UK?

Cure your onions thoroughly, then keep healthy bulbs in mesh bags, slatted trays or well-ventilated crates somewhere cool, dry and frost-free.

Can onions be stored in a shed over winter?

Yes, if the shed is dry, ventilated and protected from freezing temperatures.

How long do homegrown onions last?

Some suitable storage varieties can keep for several months, potentially until spring. Others are best used within a shorter period.

Should you wash onions before storing?

No. Remove loose, dry soil without washing or damaging the protective skins.

Why are my stored onions sprouting?

Sprouting may result from temperature fluctuations, unsuitable storage conditions or the onion naturally emerging from dormancy.

Can you eat onions that have sprouted?

Yes, provided the bulb is still sound and free from mould or rot.

Should onions be stored in the fridge?

Whole, properly cured storage onions are generally better kept in a suitable cool, dry, ventilated location. Cut onions should be refrigerated in a covered container and used promptly.

Can you store onions in a cardboard box?

Yes, if the box is suitably ventilated and kept dry. However, slatted trays and mesh bags often provide better airflow.

Why are my stored onions going soft?

Possible causes include incomplete curing, unsuitable storage conditions, physical damage, sprouting or disease.

How do you plait onions for storage?

Leave the dried foliage attached and braid several onion tops together, using string for extra support if necessary. Hang the plait in a cool, airy location.

Can autumn-planted onions last all winter?

Some may keep into early winter, but many overwintered varieties aren’t as suitable for long-term storage as spring-planted storage onions.

Can I freeze onions instead of storing them?

Yes. Chopped onions can be frozen and used later in cooked dishes.

Final Thoughts: Keeping Your Onion Harvest Fresh Through Winter

Learning how to store onions for winter in the UK is one of the most useful skills you can develop as a vegetable gardener.

After spending months growing a fantastic crop, it’s worth taking the extra time to make sure the harvest is stored correctly.

The most important thing is to choose suitable varieties, harvest them carefully and allow the bulbs to cure thoroughly.

Once the skins and necks are dry, store your onions somewhere cool, dry, frost-free and well ventilated.

Mesh bags, slatted trays, wooden crates and traditional onion plaits can all work well.

Remember to check your onions regularly, use any sprouting bulbs promptly and remove any showing signs of decay.

With the right care, you can enjoy homegrown onions in soups, stews, curries and all sorts of delicious meals long after the growing season has finished.

I hope this guide helps you make the most of your onion harvest and enjoy more homegrown food throughout winter.

Thanks for joining me here at Gardening with Ben.

Keep smiling, keep shining, keep gardening with Ben!