Tuberous begonia · Edmonton, Alberta, Canada
When to sow tuberous begonias in Edmonton
Main outdoor window
27 May - 24 Jun
The window this page is built around.
Timed from last spring frost
13 May
In Edmonton, on your chosen risk.
Ready to pick
1 Jun - 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 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.
Plant the tubers
27 May - 24 Jun
After the last frost, once the soil has warmed. This crop is never fully dormant, so it cannot be planted bare-root in winter.
In flower
1 Jun - 31 Oct
Tuberous begonias through the year
Against the frost risk in Edmonton
Why these dates
Start the tubers indoors eight weeks before the last frost, hollow side up and barely covered, then plant out a fortnight after the frost date once nights are above 10C. Starting them in warmth is not optional in a short season - planted straight outside they flower six weeks late.
Damaged at 0C and killed by any real frost. The tuber cannot survive a frozen soil at all, so lift it when the leaves yellow in autumn and store it dry and frost-free everywhere below zone 9.
Tuberous begonias are planted once and then left in place, so there is no sowing offset to resolve. Nor is there a dormant season to plant into: this crop keeps its leaves and keeps growing through the winter, which is exactly why cold damages it. The window on this page therefore waits until the last frost in Edmonton has passed and the soil has begun to warm, giving the roots the longest possible run before the cold returns.
Edmonton sits in zone 4a, which is colder than this crop is rated for, so it will need winter protection or a container that can be moved under cover. The dates below still describe the right time of year; the open question is survival rather than timing.
Also in Edmonton
Other flowers to time
Growing tuberous begonias in Edmonton
When should I plant tuberous begonias in Edmonton?
Aim for 27 May - 24 Jun in an average year. If you would rather not gamble on the weather, wait until 5 Jun - 3 Jul - by then frost has finished in nine years out of ten.
When will tuberous begonias be ready to harvest in Edmonton?
Expect to start picking around 1 Jun - 31 Oct, based on 90 to 120 days to maturity from the planting date calculated for this location.
How much frost will tuberous begonias tolerate?
Damaged at 0C and killed by any real frost. The tuber cannot survive a frozen soil at all, so lift it when the leaves yellow in autumn and store it dry and frost-free everywhere below zone 9.