Welsh onion · Brussels, Brussels Capital, Belgium
When to plant welsh onions in Brussels
Main outdoor window
16 Mar - 6 Apr
The window this page is built around.
Timed from last spring frost
13 April
In Brussels, on your chosen risk.
Ready to pick
1 Apr - 31 Oct
If you plant at the start of the window.
The average last frost. Half of all years are later than this.
Step by step in Brussels
Each window is a range, not a single day. Earlier in the range buys you a longer season; later in it buys you a safer one.
Sow direct
16 Mar - 6 Apr
Four weeks before your last frost.
Plant out
27 Apr - 18 May
Two weeks after your last frost.
Harvest
1 Apr - 31 Oct
Welsh onions through the year
Against the frost risk in Brussels
Why these dates
Very hardy, to -20C, and one of the first alliums to grow again in spring.
Seed packets and extension guides express timing as weeks either side of the last spring frost, because that is the only reference point that travels. Welsh onions are timed with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for Brussels.
Hardiness is not the obstacle here. Brussels is zone 8b, comfortably inside the range this crop is rated for, so an established plant should come through an average winter without protection.
Do not expect a crop in the first year. A plant set out now should give its first worthwhile pick around year 1, and will then produce every year after that, which is what makes the planting decision worth getting right the first time.
Also in Brussels
Other vegetables to time
Growing welsh onions in Brussels
When should I plant welsh onions in Brussels?
Aim for 16 Mar - 6 Apr in an average year. If you would rather not gamble on the weather, wait until 26 Mar - 16 Apr - by then frost has finished in nine years out of ten.
When will welsh onions be ready to harvest in Brussels?
Expect to start picking around 1 Apr - 31 Oct, based on 80 to 100 days to maturity from the planting date calculated for this location.
How much frost will welsh onions tolerate?
Very hardy, to -20C, and one of the first alliums to grow again in spring.