Last Updated on: October 25, 2026

Growing Onions All Year Round: A UK Autumn and Winter Guide

Growing onions all year round in the UK means combining seasonal crops with stored harvests. It does not mean planting ordinary onion sets every month or expecting mature bulbs throughout winter.

A practical approach is to grow suitable autumn-planted onions for an earlier summer harvest, follow with spring-planted onions for a later crop, and include salad onions to extend the picking season. Carefully dried storage onions can then supply the kitchen during the colder months.

Autumn and winter are important parts of this plan. They provide opportunities to establish overwintering varieties, prepare beds, check stored bulbs and organise the next season’s planting.

Whether you garden on an allotment, in raised beds or in containers, choosing suitable varieties and responding to the weather will help you build a longer supply of home-grown onions.

Can You Grow Onions All Year Round in the UK?

You can have onions growing during much of the year and aim for a long supply in the kitchen. However, the type of crop and the jobs involved change with the seasons.

Bulb onions generally mature during summer or early autumn. Suitable varieties can then be dried and stored for later use.

Overwintering onions remain in the ground through the colder months, but they normally produce their mature bulbs the following summer. They are not usually a source of full-sized onions in December or January.

Salad onions offer another option because they are harvested young for their tender stems and leaves.

A useful year-round plan combines:

• Autumn-planted onions for an earlier bulb harvest.
• Spring-planted onions for a later crop.
• Salad onions for additional fresh harvests.
• Stored bulbs for autumn and winter cooking.

How closely this meets your household’s needs depends on your growing space, harvest size, storage conditions and how many onions you use.

Choose the Right Onions for Each Season

Different onions suit different planting windows. Check the variety and supplier’s instructions before planting.

Autumn and Overwintering Onions

These varieties are suitable for establishing in autumn and remaining outdoors through winter.

They develop roots and foliage before growth slows in cold weather. As temperatures rise in spring, they begin growing more strongly again.

They are sometimes described as Japanese or overwintering onions. Choose stock specifically recommended for autumn planting rather than using an ordinary spring variety.

Spring-Planted Bulb Onions

Spring onions grown for mature bulbs can be planted as sets or raised from seed.

These generally provide a later harvest than overwintering onions. If your main aim is supplying the kitchen through winter, look for varieties described as suitable for storage.

Remember that “spring-planted bulb onions” and “salad onions” are different growing plans, even though the names can cause confusion.

Salad Onions

Salad onions, also called spring onions or scallions, are harvested while young.

Their name does not restrict them to spring planting. Different varieties suit different sowing times, with hardy varieties useful for late-summer or autumn establishment.

Read the packet carefully, particularly when planning an overwintered crop.

A Year-Round Onion Growing Calendar

Use this calendar as a starting point and adjust it to your local conditions.

Time of year	Main onion jobs
January–February	Check stored bulbs, plan the next crop and sow suitable onion seeds under appropriate conditions
March–April	Plant spring sets when the ground is suitable and begin seasonal salad onion sowings
May	Weed, check moisture and look after growing crops
June–July	Harvest overwintered onions as they mature
August–September	Harvest later bulb onions and dry suitable crops for storage
September–October	Plant suitable autumn sets and sow hardy salad onions where recommended
November–December	Monitor overwintering crops, drainage and stored bulbs

These dates are flexible. A cold spring or wet autumn can delay planting.

The condition of the ground matters more than planting on a particular weekend.

When to Plant Autumn Onion Sets

September and October are common planting months for overwintering onion sets. Some planting stock is also suitable for November.

Follow the instructions supplied with your chosen variety.

Aim to plant into workable soil with reliable drainage. Avoid pushing sets into saturated ground simply because the calendar suggests it is time.

On an exposed Sheffield or Yorkshire allotment, conditions may differ considerably from those in a sheltered southern garden.

If your bed regularly becomes waterlogged during winter, consider a raised bed or concentrate on spring planting instead.

Autumn planting is an option, rather than something every gardener needs to do.

Can You Plant Onions During Winter?

Winter planting is possible only when both the variety and conditions are suitable.

December and January should not automatically be treated as replacements for an autumn planting window. The ground may be frozen, saturated or difficult to prepare without damaging its structure.

Before planting, check that:

• The supplier recommends that planting time.
• The soil drains freely.
• The sets are firm and healthy.
• You can work without compacting the bed.
• The planting area receives sufficient sunlight.

If the ground is unsuitable, starting appropriate sets in modules may provide a temporary alternative.

However, avoid leaving them in small modules for so long that their roots become congested.

Prepare a Suitable Growing Bed

Choose a sunny position with soil that does not hold standing water.

Clear perennial weeds before planting. Onion foliage leaves plenty of open ground where weeds can establish, so careful preparation reduces later work.

Add well-rotted organic matter where needed to improve soil condition. Avoid fresh manure directly around the bulbs.

Prepare a surface that allows each set to be planted without forcing it into hard ground.

Do not repeatedly cultivate wet soil in an attempt to make it ready. Allow it to drain first.

For no-dig beds, plant into a suitable, well-prepared growing layer and keep large pieces of undecomposed material away from the sets.

Leave enough access to inspect the crop without walking on the bed.

How to Plant Autumn Onion Sets

Plant each set with the flatter rooting end downwards and the pointed end upwards.

The tip should just show above the soil surface.

Allow approximately 10–15cm between sets and 20–30cm between rows, unless the supplier recommends different spacing.

Wider spacing gives individual bulbs more room, while sensible row spacing makes weeding easier.

Planting Step by Step

1. Mark your rows or planting positions.
2. Make a shallow hole for each set.
3. Place the set upright without damaging its base.
4. Draw soil around the bulb.
5. Firm gently while leaving the tip visible.
6. Water if needed to settle dry soil.
7. Label the variety and planting date.

Do not peel the bulbs or cut them into pieces.

Check the bed after planting because birds sometimes disturb sets before they root. Replant displaced bulbs promptly.

Looking After Onions Through Winter

Winter care is mainly about checking the crop and maintaining suitable conditions.

Slow growth is normal during cold weather. It does not automatically mean that the plants need fertiliser.

Check Drainage After Heavy Rain

Look for patches where water remains around the plants.

Persistent waterlogging can damage roots and encourage rot. Record troublesome areas so you can change the growing method or bed layout in future.

Avoid digging around established plants while the ground is saturated.

Remove Weeds While They Are Small

Hand-weed carefully near onions to avoid disturbing their roots.

A short session during suitable weather is easier than removing large weeds from among the crop in spring.

Inspect After Frost and Strong Winds

Check for lifted plants, disturbed sets and damaged covers.

Gently resettle displaced plants when the ground becomes workable. Avoid pressing down on frozen or saturated soil.

Water According to Conditions

Outdoor onions may receive enough winter rain without additional watering.

Plants in containers or under cover need separate checks. Their compost may dry out even when the outdoor beds remain wet.

Should You Cover Onions in Winter?

Suitable overwintering onions do not normally need a heated greenhouse.

Temporary protection can help during establishment or exceptionally harsh weather, but permanent covering changes the growing conditions.

A cloche keeps off some rainfall, so check moisture underneath it. Ventilate during suitable weather and avoid trapping persistent dampness around the foliage.

Secure any cover properly so that wind cannot lift it onto the crop or neighbouring beds.

If using netting, keep it taut and inspect it regularly.

Protection cannot compensate for unsuitable planting stock or poor drainage.

Growing Autumn Onions in Containers

Containers are useful where garden soil is too wet or growing space is limited.

Choose a broad container with drainage holes and enough room to maintain sensible spacing.

Use suitable peat-free container compost and place the pot in a sunny position.

During winter:

• Keep drainage holes clear.
• Avoid water-filled saucers.
• Check moisture beneath the compost surface.
• Secure pots against being knocked over.
• Inspect plants after severe weather.

Containers can become saturated during prolonged rain, but sheltered pots may also dry unexpectedly.

Check each container rather than assuming they all need the same treatment.

Feeding Overwintered Onions in Spring

As conditions improve, healthy plants should begin growing more strongly.

Assess the bed before feeding. Consider its fertility, previous compost applications and the instructions for any fertiliser you intend to use.

A suitable feed may help where nutrients are limited, but repeated strong applications are unnecessary.

Pale foliage does not always indicate hunger. Waterlogging, root damage and disease can produce similar symptoms.

Check the growing environment before adding more fertiliser.

Avoid excessive feeding later in the season, when the crop should be moving towards maturity.

Keep a record of products and application dates so that different feeds do not accidentally overlap.

Plant a Spring Crop for Later Harvests

Autumn onions provide an earlier harvest, but a spring crop helps extend your supply.

Reserve space for spring sets or seed-raised plants.

Choose varieties according to how you will use them. A smaller early crop for immediate cooking and a larger planting of storage varieties may be more useful than equal quantities of everything.

Label each planting clearly.

This helps you distinguish onions intended for earlier use from those you hope to keep.

Leave room for weeding and harvesting, particularly where neighbouring crops will become larger during summer.

Include Salad Onions for Fresh Picking

Salad onions are useful because they can be harvested young.

During suitable growing weather, make small sowings at intervals rather than sowing a large quantity that becomes ready together.

For overwintering, choose a hardy variety and follow its recommended sowing dates.

Cold weather and low light slow growth considerably. An autumn-established crop may provide an early spring harvest, but a late winter sowing will not grow at summer speed.

A sheltered growing area may help, although it does not remove the limits imposed by short days.

Keep notes on which sowings perform well on your plot.

Harvest Autumn-Planted Onions When They Mature

Overwintered bulb onions are generally ready during early summer, depending on the variety and weather.

Watch for natural yellowing and toppling of the foliage.

Do not deliberately bend the leaves to force ripening.

Lift carefully when the crop is ready, avoiding bruising or damaging the bulbs. Choose a dry spell where possible.

Keep damaged or bolted onions separate and use them promptly if they remain sound.

Once the bed is clear, inspect the crop debris for signs of disease before deciding what to plant next.

Store Onions for Autumn and Winter Cooking

Storage is a major part of extending your home-grown onion supply.

Dry suitable bulbs in a sheltered, airy place. Spread them out rather than piling freshly harvested onions together.

Allow the necks and outer skins to dry thoroughly before selecting bulbs for storage.

Keep only sound, undamaged onions for longer storage.

Use a dry, ventilated space and avoid sealed plastic bags. Inspect the bulbs regularly and remove any showing signs of deterioration.

Use sound onions that begin to sprout first. Discard those showing rot.

Storage life varies with the variety, growing conditions and drying process. Not every autumn-planted onion will keep as long as a variety selected specifically for storage.

Common Mistakes to Avoid

Planting the Wrong Variety for the Season

Choose autumn stock for autumn planting and spring stock for spring, unless the supplier states otherwise.

Expecting Mature Bulbs Throughout Winter

Overwintering onions normally mature the following summer. Stored bulbs usually provide winter supplies.

Growing Too Many Early Onions

A large crop with limited storage potential may be difficult to use. Match planting quantities to your household.

Ignoring Winter Wetness

Poor drainage can undermine an otherwise well-planned crop.

Feeding Whenever Growth Slows

Seasonal slowdown is normal. Extra fertiliser does not replace warmth, light or healthy roots.

Forgetting Stored Bulbs

Check stored onions regularly so that deteriorating bulbs can be removed promptly.

Frequently Asked Questions

Can I Plant Onion Sets Every Month?

No. Bulb onions have seasonal planting windows, and the variety must suit the timing.

Are Winter Onions Harvested in Winter?

Usually not. The term generally describes onions that remain growing through winter before maturing the following summer.

Can Autumn Onions Grow in a Polytunnel?

Yes, but consider ventilation, watering and when the space will be needed for later crops. The onions may still occupy the bed when spring planting begins.

Do Autumn Onions Need Daily Watering?

No. Check conditions and water when necessary. Outdoor rainfall may provide enough moisture through winter.

Can I Follow This Plan in a Small Garden?

Yes. Grow smaller quantities, use suitable containers and prioritise the onions your household uses most.

Can I Guarantee a Full Year’s Supply?

No. Weather, disease, storage losses and household demand all affect the result. Start with a manageable plan and adjust it using your own harvest records.

Build a Longer Home-Grown Onion Season

A useful onion plan combines autumn planting, a later spring crop, selected salad onions and careful storage.

Choose varieties for their intended purpose and adjust planting to the conditions on your plot.

Good drainage, clear labels and a few notes about harvest size and storage performance will help you improve the plan each year.

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