How to Grow

How to Grow Spring Onions in the UK

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Spring onion (Allium fistulosum)

Freshly pulled spring onions with white bases and green tops on a board. Photo: Kolforn, CC BY-SA 4.0, via Wikimedia Commons.

9 sources cited · Verified

The short answer

Plant
Early March to late September
Ready in
60–60 days
Site
5+ hours of sun, soil pH 6.6–7.4
Biggest risk
Onion downy mildew

In the UK, spring onions go in the ground early March to late September, and are ready to harvest 60–60 days after planting.

Spring onions (Allium fistulosum) — Grown as a fast annual salad crop, pulled young within about two months of sowing.

Core growing advice on this page is checked against named horticultural and university-extension sources — see References.

Watch: Growing Spring Onions at Home

A step-by-step SoilCommander video on growing perfect spring onions at home in the UK — sowing, spacing, care and harvest.

Companion Planting

avoid shared disease

Allium sativum

Both crops are documented hosts of Onion downy mildew. These pathogens persist in soil for many years -- RHS gives up to 20 years for club root resting spores, at least 15 years for allium white rot sclerotia, and advises a five-year gap before replanting onions or shallots after downy mildew --…

avoid shared disease

Allium cepa

Both crops are documented hosts of Onion downy mildew. These pathogens persist in soil for many years -- RHS gives up to 20 years for club root resting spores, at least 15 years for allium white rot sclerotia, and advises a five-year gap before replanting onions or shallots after downy mildew --…

avoid shared disease

Allium cepa Aggregatum Group

Both crops are documented hosts of Onion downy mildew. These pathogens persist in soil for many years -- RHS gives up to 20 years for club root resting spores, at least 15 years for allium white rot sclerotia, and advises a five-year gap before replanting onions or shallots after downy mildew --…

Quick Facts

Factor Value
Soil pH 6.6 - 7.4
Sunlight 5-5 hours direct sun
Optimal growing temp 12-25C
Time to harvest 60-60 days
Drainage RHS: "Choose a sunny planting site" with "free-draining soil", improved with organic matter.
Lifecycle Grown as a fast annual salad crop, pulled young within about two months of sowing; botanically a hardy biennial to short-lived perennial. Hardy types overwinter to crop the following spring, and plants left in the ground form clumps and flower in a later year.
Edible parts whole young plant (leaves and bulb)

At a Glance

Allium fistulosum Spring onion Onion downy mildew Leek moth Onion fly Allium leaf miner Stem and bulb nematode DISEASES PESTS

Regional Planting Calendar

Region Sow
Southern England early March to late September
Midlands derived mid March to mid September
Northern England derived early April to early September
Scotland derived mid April to early September

Rows marked derived are interpolated between regions our sources do state, because no source we consulted gives a figure for that region specifically. They are deliberately wider to reflect that uncertainty.

Southern England - detail & sources

Sow small batches every couple of weeks from March through to about September for a continuous supply; sow hardy varieties in late summer/early autumn to overwinter for a spring crop. Southern England has the UK's earliest soil-warming and last frosts (Met Office), so the earliest March sowings and the longest season apply here.

Midlands - detail & sources

DERIVED: the successional sowing window opens about two weeks later than southern England and closes a little earlier, as the Midlands warm later and cool sooner (Met Office south-to-north gradient). Hardy autumn sowings still overwinter for spring.

Northern England - detail & sources

DERIVED: sowing starts about a month later than southern England (from April) and ends by early September, reflecting the Met Office south-to-north gradient. Start under cover for an earlier crop.

Scotland - detail & sources

DERIVED: the latest and shortest window - sow from about mid-April to early September, as Scotland is slowest to warm and cools earliest (Met Office). Modules under cover extend the season at both ends.

Soil & Growing Conditions

Rows of spring onions growing in ridged soil in a field — "Bunching onions growing in a field" by Miyuki Meinaka is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Bunching onions growing in a field” by Miyuki Meinaka is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

Water: RHS: water young plants until established, "then only water during prolonged dry spells"; container plants need more frequent watering. Univ. of Maryland: "Ensure ample moisture, especially after bulbs begin enlarging".

Soil pH range

6.6 7.4

Span reflects genuine variation between the cited authorities, not a single agreed figure.

Growth Stages

Stage BBCH Notes
Sowing & Germination 0 Spring onions are almost always sown direct where they are to grow. SOWING DEPTH & SPACING: make a shallow drill 1cm (half inch) deep, water along the base, and sow the seed thinly, spacing rows about 20cm (8in) apart; thin seedlings to about 2.5cm (1in) apart. TIMING: sow small batches every couple of weeks from March onwards for a continuous supply through spring, summer and autumn; sow hardy varieties in late summer to early autumn to overwinter for a spring crop. An earlier start is possible from a March sowing in modular trays under cover, and they also grow well in a container at least 30cm (1ft) wide.
Leaf & Shank Growth 3 Each seedling grows into a slim plant with hollow green leaves and a slender white shank, barely swelling at the base. Water young plants until they are well established, then only during prolonged dry spells (container plants need watering more often as the compost dries quickly). Weed regularly - hoe between the rows and hand-weed between the closely spaced plants - so the shallow-rooted onions are not crowded.
Harvest 8 Spring onions generally take about two months (roughly eight weeks) to reach harvesting size. Pull them young and mild when about 15cm (6in) tall with the base no more than 1-2.5cm (half to 1in) across - simply lift individual onions with a hand fork whenever you need them, right through spring to autumn. Harvest regularly and successionally rather than all at once, as they do not store and are best eaten fresh.
Bolting, Flowering & Overwintering 6 Spring onions are grown as a quick crop, but plants left in the ground eventually run up a round white flowerhead (bolting), after which the shanks turn tough - so pull them before this. Hardy varieties sown in late summer or early autumn simply sit through the winter and are pulled the following spring, while Allium fistulosum left to grow on forms a perennial clump that flowers each year and can be divided.

Harvest & Storage

A crate of bunched red and white salad onions at a market — "Spring onions at a market in Gallicano" by Kritzolina is licensed under CC BY-SA 4.0. Source: Wikimedia Commons
“Spring onions at a market in Gallicano” by Kritzolina is licensed under CC BY-SA 4.0. Source: Wikimedia Commons.

When to pick: RHS: pull salad onions when "about 15cm (6in) tall, with the bulb no more than 1-2.5cm (½-1in) across". Univ. of Maryland independently agrees on the same benchmark: "Harvest green onions when tops are 6 inches tall".

Diseases

Onion downy mildew
moderate

Peronospora destructor

RHS names "salad onions" (spring onions) among affected hosts.

Pests

Leek moth
moderate

Acrolepiopsis assectella

RHS: affects "Leek, onion, shallot, garlic". [Allium genus-wide RHS pest pages explicitly name multiple Allium crops including chives/shallot; reused for other Allium species in the graph.]

Onion fly
moderate

Delia antiqua

RHS onion fly page: affects "Onion, shallots, and leeks". [Allium genus-wide RHS pest pages explicitly name multiple Allium crops including chives/shallot; reused for other Allium species in the graph.]

Allium leaf miner
high

Phytomyza gymnostoma

RHS: affects "Leeks, onion, chives, shallot and garlic". [Allium genus-wide RHS pest pages explicitly name multiple Allium crops including chives/shallot; reused for other Allium species in the graph.]

Stem and bulb nematode
high_where_present

Ditylenchus dipsaci

RHS names onions among affected vegetables; Allium family members "swell and distort (onion blout)". [Allium genus-wide RHS pest pages explicitly name multiple Allium crops including chives/shallot; reused for other…

References

  1. Tier 1. Primary UK source: sow direct 1cm deep, rows 20cm apart, thin to 2.5cm; succession every couple of weeks from March; hardy varieties late summer/autumn for spring; water until established then only in dry spells; weed; harvest at about 15cm tall, base 1-2.5cm, in roughly two months.

  2. Tier 1. US extension corroboration for direct sowing, thin spacing, moisture needs and succession sowing of bunching/salad onions.

  3. Tier 1. Host-specific foliar disease (Peronospora destructor) of alliums favoured by cool, wet, humid weather.

  4. Tier 1. Host-specific pest: larvae mine leaves; secondary rots make the crop inedible; widespread across England since 2002.

  5. Tier 1. Host-specific pest of alliums: caterpillars mine leaves; mainly southern/eastern England and spreading.

  6. Tier 1. Host-specific pest: maggots damage roots and bases of alliums; most damaging June-July.

  7. Tier 1. Host-specific pest (Ditylenchus dipsaci): causes swollen, distorted "bloat" growth; persists in soil and on seed.

  8. Tier 1. UK climate context for the south-to-north spring gradient used to derive regional successional sowing windows.

  9. Tier 1. International agronomic ranges (temperature, pH) for the bunching onion.

9 independent sources are cited for this crop. Where they disagree - soil pH is the clearest case - every figure is preserved rather than averaged into false precision.

Frequently Asked Questions

When should I sow spring onions in the UK?

In southern England, from early March. In northern England and Scotland, wait until early April. Treat these as a guide rather than a fixed date — the governing rule is to sow only once frost risk has passed and temperatures are reliably warm enough.

When do I sow spring onions?

Sow early March to late September.

How long do spring onions take to grow?

Typically 60–60 days, depending on cultivar and growing conditions.

What soil pH do spring onions need?

A pH of about 6.6–7.4. That span reflects genuine variation between the authorities we cite rather than a single agreed figure — the References section lists each source's exact range.

What problems affect spring onions?

Our data links 1 disease and 4 pests to this crop. See the sections above for each one and how to manage it.

Plan next season before the problems start

Most of the advice on this page comes down to timing and spacing — sowing at the right moment, rotating beds, and giving plants enough airflow. The UK Garden Planner lays your plot out month by month so those decisions are already made before the season starts.

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SoilCommander Editorial Team

UK vegetable growing guides · Checked against RHS & Met Office guidance

Every SoilCommander guide is written and maintained by our editorial team for real UK growing conditions, and reviewed against Royal Horticultural Society growing advice and Met Office climate data before publication.

Vegetable Growing Guides UK

Last verified 2026-07-31

Sowing and harvest timings for spring onions sit alongside every other crop in the UK vegetable planting calendar. For the wider job list in its main March window, see what to plant in March in the UK.

Quick answer

How To Grow Spring Onions In The UK

To grow spring onions in the UK, sow thinly in drills or containers from spring onwards, keep seedlings watered, and harvest young stems as soon as they are large enough to use. Spring onions fit well between slower crops because they take little space and can be sown in repeat batches.

Succession crop Sow small rows every few weeks instead of one large batch.
Space saver Use bed edges, containers, and gaps between slower-growing vegetables.
Harvest young Pull when stems are usable and tender so the crop keeps moving through the season.
Watch the spring onion growing guide

This video supports the page with a practical look at sowing and growing spring onions at home, especially for small spaces and repeat sowings.

Watch the spring onion video on YouTube

Use the UK vegetable planting calendar to plan repeat sowings. Use the UK Vegetable Garden Planner PDF to track small-space sowings, harvests, and follow-on crops.

Relevant next steps

Tools That Help With This Crop

Use these links when the guide moves from reading into sowing, planting, watering, and keeping the crop healthy.

Hand tools for plantingUseful for sowing, transplanting, weeding, and bed maintenance. Soil and plant carePrepare beds, feed plants, and support stronger crop growth. Watering equipmentKeep seedlings, containers, raised beds, and summer crops consistent.
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