Welsh Onion (Allium fistulosum)
2 sources cited · Verified
The short answer
- Plant
- Early March to early September
- Site
- 6+ hours of sun, soil pH 6.2–6.8
- Biggest risk
- Allium white rot
In the UK, welsh onions go in the ground early March to early September.
Welsh onions (Allium fistulosum) — bulbous herbaceous perennial.
Timing is the decision that matters most in the UK: there are 4 separate regional sowing windows, ranging from early March in Southern England to early March in Scotland.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
Regional Planting Calendar
| 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 pH | 6.2 - 6.8 |
| Sunlight | 6-6 hours direct sun |
| 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)
Soil pH range
Span reflects genuine variation between the cited authorities, not a single agreed figure.
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
References
-
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.
-
Hardiness H3 (hardy in coastal/relatively mild UK areas, tolerates -5 to 1C). 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.
2 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 soil pH do welsh onions need?
A pH of about 6.2–6.8. 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 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.
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Last verified 2026-08-28
Where To Go From Here
Take this crop from reading into a written plan for your own beds.
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.