Welsh Onion (Allium fistulosum)
2 sources cited · Verified
The short answer
- Site
- 6+ hours of sun, soil pH 6.2–6.8
- Biggest risk
- Allium white rot
Welsh onions (Allium fistulosum) — bulbous herbaceous perennial.
Unlike an annual crop, the work here is front-loaded into establishment: get the planting and the site right and the same plants crop for several seasons.
Core growing advice on this page is checked against named horticultural and university-extension sources — see References.
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. |
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
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
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
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