How to Grow Welsh Onions
On this page
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 sources — see References.
Welsh Onion (Allium fistulosum)
3 sources cited · Verified
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. |
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
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
Timing for Welsh Onions follows soil temperature and frost, not the calendar date. The Global vegetable planting calendar explains the method. 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.
Sources
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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.
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PFAF entry for Allium fistulosum. Fetched and parsed directly for the USDA hardiness rating.
These 2 sources are specific to this region. The full list of 3 sources behind this guide (Johnny's Selected Seeds, Plants For A Future (PFAF), Royal Horticultural Society) is in the references of our UK guide to welsh onions; they describe the plant itself, which is the same wherever it grows.
Frequently Asked Questions
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
This page gives you the thresholds; the planner turns them into your own calendar. It works from what you can observe and measure in your garden rather than from dates written for somebody else’s latitude.
Get the Global Garden Planner →Instant PDF download · Works in either hemisphere
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 international horticultural research and extension sources. 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
Related guides
More from the same group (the onion family):
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.