When to plant Onion (Sets) in the UK
Onion (Sets) is normally planted as sets, the small part-grown bulbs rather than sown from seed — sets are quicker and less fiddly than seed — so the dates below are for planting and harvest, not sowing.
Planting and harvest dates by region
Timings below are adjusted from the midlands and lowland wales baseline using Met Office average last and first frost dates for each area.
| Where you are | Plant out | Harvest |
|---|---|---|
| South West Coast and Cornwall | mid April to mid May | early July to early September |
| South Coast and Channel | early April to early May | early July to early September |
| Greater London (Urban Heat Island) | mid April to early May | early July to early September |
| South East and Home Counties | late March to mid April | early July to early September |
| East Anglia | mid March to mid April | early July to early September |
| Midlands and Lowland Wales | mid March to mid April | early July to early September |
| Wales and West Coast | late March to late April | early July to early September |
| Northern England | early March to early April | early July to early September |
| Scotland Lowlands and Central Belt | late February to late March | early July to early September |
| Scotland Highlands and Islands | early February to early March | early July to early September |
| Northern Ireland | late March to mid April | early July to early September |
| Channel Islands and Isle of Man | mid April to mid May | early July to early September |
Growing notes
Overwintering (autumn-planted) sets go in around October for an earlier July harvest; spring-planted sets go in March-April for harvest from August. This entry models the common spring-planted crop.
At a glance
- Spacing
- 10 cm between plants
- Row spacing
- 25 cm
- Plants per m²
- 40
- Days to maturity
- 140 days
- Yield per plant
- 0.12 kg
- Sun
- Full sun
- Frost tender
- No
- Grows in a container
- Yes, 20 litres or more
- Minimum soil depth
- 20 cm
- Balcony rating
- 3 out of 5
What usually goes wrong
- bolting
- onion downy mildew
- birds pulling up sets
- onion neck rot in storage
Companion planting
Grows well near
Keep away from
Related guides
Timings cross-checked against RHS guidance for onion (sets).