Onion · Edmonton, Alberta, Canada
When to plant onions in Edmonton
Main outdoor window
15 Apr - 6 May
The window this page is built around.
Timed from last spring frost
13 May
In Edmonton, on your chosen risk.
Ready to pick
24 Jul - 13 Aug
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 Edmonton
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.
Start indoors
4-25 Mar
Ten weeks before your last frost, under cover or on a windowsill.
Plant out
15 Apr - 6 May
Four weeks before your last frost.
Harvest
24 Jul - 13 Aug
Onions through the year
Against the frost risk in Edmonton
Why these dates
Start seed ten weeks before last frost. Choose long-day cultivars above roughly 38 degrees latitude and short-day types below it - the wrong choice produces no bulb regardless of timing.
Young plants take -8C. Autumn-planted sets overwinter reliably in zone 6 and warmer.
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. Onions are timed from 10 weeks before that frost for an indoor start, with planting out 4 weeks before it, and this page simply resolves those offsets against the frost date computed for Edmonton.
The median frost-free season here is 137 days, against 100 to 120 days to maturity for this crop counted from planting out. That margin is what decides whether a late sowing is worth attempting.
Also in Edmonton
Other vegetables to time
Growing onions in Edmonton
When should I plant onions in Edmonton?
Aim for 15 Apr - 6 May in an average year. If you would rather not gamble on the weather, wait until 24 Apr - 15 May - by then frost has finished in nine years out of ten.
When will onions be ready to harvest in Edmonton?
Expect to start picking around 24 Jul - 13 Aug, based on 100 to 120 days to maturity from the planting date calculated for this location.
How much frost will onions tolerate?
Young plants take -8C. Autumn-planted sets overwinter reliably in zone 6 and warmer.