How to Grow Welsh Onions UK
On this page
- Welsh Onion (Allium fistulosum)
- When to Plant Welsh Onions in the UK
- Quick Facts
- At a Glance
- Soil & Growing Conditions
- Growth Stages
- Harvest & Storage
- Diseases
- Pests
- Welsh Onion, Field Row to Blanched Bunch
- Plan your Welsh Onions planting
- Growing Welsh Onion in another region
- References
- Frequently Asked Questions
In the UK, welsh onions go in the ground early March to early September.
Timing is the decision that matters most in the UK: sowing early March, and that same window applies across all 4 regions covered here.
The short answer
- Plant
- Early March to early September
- Biggest risk
- Allium white rot
Core growing advice on this page is checked against named horticultural sources — see References.
Welsh Onion (Allium fistulosum)
3 sources cited · Verified
When to Plant Welsh Onions in the UK
When to plant Welsh onions in the UK: in Southern England, sow early March to early September. Find your area in the table below.
| Region | Sow |
|---|---|
| Southern England | early March to early September |
| Midlands | early March to early September |
| Northern England | early March to early September |
| Scotland | early March to early September |
Southern England - detail & sources
Neither source gives region-specific UK dates; RHS gives a UK-wide hardiness rating (H3) with no frost-chasing urgency described for this hardy perennial, so one window covering the early-spring-through-late-summer sowing range (Johnny's Selected Seeds) is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Midlands - detail & sources
Neither source gives region-specific UK dates; RHS gives a UK-wide hardiness rating (H3) with no frost-chasing urgency described for this hardy perennial, so one window covering the early-spring-through-late-summer sowing range (Johnny's Selected Seeds) is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Northern England - detail & sources
Neither source gives region-specific UK dates; RHS gives a UK-wide hardiness rating (H3) with no frost-chasing urgency described for this hardy perennial, so one window covering the early-spring-through-late-summer sowing range (Johnny's Selected Seeds) is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Scotland - detail & sources
Neither source gives region-specific UK dates; RHS gives a UK-wide hardiness rating (H3) with no frost-chasing urgency described for this hardy perennial, so one window covering the early-spring-through-late-summer sowing range (Johnny's Selected Seeds) is applied across all four sub-regions rather than inventing a north/south gradient the sources do not support.
Quick Facts
| Factor | Value |
|---|---|
| Soil texture | chalk, loam or sand (RHS) |
| Drainage | well-drained |
| Lifecycle | bulbous herbaceous perennial |
| Edible parts | leaves, stems, bulbs |
At a Glance
Soil & Growing Conditions
Water: moist but well-drained (RHS)
Growth Stages
| Stage | BBCH | Notes |
|---|---|---|
| Sowing | 0 | Direct seed 1/4-1/2 inch deep in 2-3 inch wide bands; sow early spring for summer harvest or July-August for fall/overwintered spring harvest (Johnny's Selected Seeds). |
| Establishment and clump growth | 3 | Clump-forming perennial with hollow, strap-shaped leaves, staying green virtually all year round; grows in full sun on fertile, moist but well-drained soil (RHS). |
| Hilling and blanching | 3 | Hill soil around the plants 2-3 times during growth to blanch the stalks and increase the edible white portion (Johnny's Selected Seeds). |
| Flowering | 6 | Creamy-white flowers in mid-summer (RHS); remove spent flower stems and foliage as maintenance. |
Harvest & Storage
When to pick: Loosen the clump with a fork and gather stems once hilled and blanched to the desired white-shank length; wash, hydrocool and store near freezing after harvest (Johnny's Selected Seeds). Sown in early spring for a summer harvest, or in July-August for a fall or overwintered spring harvest.
Diseases
Pests
Welsh Onion, Field Row to Blanched Bunch
Plan your Welsh Onions planting
When to sow and plant Welsh Onions depends on your own frost dates. Check the UK vegetable planting calendar. To work out where it fits in your beds, sketch your plot in the free Garden Layout Planner.
Growing Welsh Onion in another region
Sowing dates, frost timing and local advice differ by country. Use the guide for where you garden.
References
-
A commercial grower reference rather than a university or horticultural authority, used for sowing/spacing/harvest specifics RHS does not cover, not contradicted by any higher authority. Sow in early spring for summer harvest, or July-August for fall/spring use. Direct seed 1/4-1/2 inch deep in 2-3 inch wide bands, thin to 1 inch apart if a larger diameter is wanted. Transplants: 6-8 seeds per cell, spaced 6-8 inches apart in rows 18 inches apart (or 6 inches apart in 24-inch rows for negi-style scallions); subtract 10-15 days from direct-seed maturity times when using transplants. Soil pH 6.2-6.8 preferred. Harvest by loosening plants with a fork and gathering; wash, hydrocool and store near freezing after harvest. Hill soil around plants 2-3 times during growth to blanch the stalks and increase the edible white portion. Extra-hardy varieties can overwinter where soil drains well.
-
PFAF entry for Allium fistulosum. Fetched and parsed directly for the USDA hardiness rating.
-
Hardiness H3 (hardy in coastal/relatively mild UK areas, tolerates -5 to 1°C). Full sun; south or west-facing aspect. Soil: chalk, loam or sand; moist but well-drained; pH acid/alkaline/neutral. Height 0.5-1m, spread 0.1-0.5m. Time to maturity 2-5 years. Edible, bulbous perennial, remaining green virtually all year round. Creamy-white flowers in mid-summer. Grows easily in fertile, well-drained soil. Propagated by seed. Maintenance: remove spent flower stems and foliage. PESTS: susceptible to allium leaf miner and onion fly. DISEASES: may develop onion white rot and onion downy mildew -- named directly for this species, not inferred.
3 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 welsh onions in the UK?
In Southern England, from early March. In Scotland, wait until early March. 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 welsh onions?
Sow early March to early September.
What problems affect welsh onions?
Our data links 2 diseases and 2 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.
Get the UK Garden Planner →Instant PDF download · Written for UK growing conditions
How this guide is put together
The growing data on this page — sowing windows, pests, diseases, soil and site requirements — comes from named horticultural sources, listed in References below, checked against RHS and Met Office guidance. An automated pipeline assembles that verified data into the page you're reading: it selects which facts to lead with and builds the surrounding prose and layout. It does not invent a date, a source or a number — where a verified value for a field isn't available, the page leaves it out rather than guessing. A person reviews and publishes each page; nothing goes live unverified.
Last verified 2026-08-28
Plan Welsh Onions by month
The months this guide gives for sowing or planting, each with the full list of jobs for that month in the UK:
- What to plant in March
- What to plant in April
- What to plant in May
- What to plant in June
- What to plant in July
- What to plant in August
- What to plant in September
More from the same group (the onion family):
Growing advice for your part of the UK
Timing and conditions change a lot inside one country. These guides cover frost dates and growing seasons region by region.
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
Keep going
Plan the next step
Use the printable SoilCommander planner for your region to turn this guide into sowing dates, bed layouts and weekly garden tasks.