When to sow Welsh Onion in the UK
Welsh Onion is sown to the calendar rather than to the frost, so the window is much the same wherever you garden in the UK.
Sowing and harvest dates by region
Welsh Onion is grown to the calendar rather than to the frost, so the same dates apply across the whole UK and every region below reads the same. Where a plant’s timings do follow the frost, Plot shifts them from the Midlands and Lowland Wales baseline using Met Office average frost dates.
| Where you are | Sow indoors | Sow outdoors | Plant out | Harvest |
|---|---|---|---|---|
| South West Coast and Cornwall | early March to late March | early April to late May | early May to late June | early March to late October |
| South Coast and Channel | early March to late March | early April to late May | early May to late June | early March to late October |
| Greater London (Urban Heat Island) | early March to late March | early April to late May | early May to late June | early March to late October |
| South East and Home Counties | early March to late March | early April to late May | early May to late June | early March to late October |
| East Anglia | early March to late March | early April to late May | early May to late June | early March to late October |
| Midlands and Lowland Wales | early March to late March | early April to late May | early May to late June | early March to late October |
| Wales and West Coast | early March to late March | early April to late May | early May to late June | early March to late October |
| Northern England | early March to late March | early April to late May | early May to late June | early March to late October |
| Scotland Lowlands and Central Belt | early March to late March | early April to late May | early May to late June | early March to late October |
| Scotland Highlands and Islands | early March to late March | early April to late May | early May to late June | early March to late October |
| Northern Ireland | early March to late March | early April to late May | early May to late June | early March to late October |
| Channel Islands and Isle of Man | early March to late March | early April to late May | early May to late June | early March to late October |
Growing notes
A clump-forming perennial onion, also sold as Japanese bunching onion, grown for its hollow leaves and thick stems rather than a bulb; it stays green almost all year and is cut as needed. Raise from seed in spring or split established clumps, and lift and divide every few years.
At a glance
- Spacing
- 20 cm between plants
- Row spacing
- 25 cm
- Plants per m²
- 20
- Days to maturity
- 120 days
- Yield per plant
- 0.1 kg
- Sun
- Full
- Frost tender
- No
- Grows in a container
- Yes, 10 litres or more
- Minimum soil depth
- 20 cm
- Balcony rating
- 4 out of 5
What usually goes wrong
- allium leaf miner
- onion fly
- onion white rot
- onion downy mildew
Companion planting
Grows well near
Keep away from
Related guides
Timings cross-checked against RHS guidance for welsh onion.