GreenlyWhen to plant watermelon in Ottawa
In Ottawa, watermelon: sow seedlings around 19 April for the greenhouse and around 10 May for open ground; plant into a greenhouse around 21 May; plant out into open ground around 11 June.
Last spring frost around 30 April, first autumn frost around 1 November. Frost-free days: 185 days.
The dates follow the Greenly calendar: open ground a week after the last frost once the soil is warm enough for the crop, frost-hardy crops three weeks before it, an unheated greenhouse three weeks earlier, seedlings sown so they are ready on the day. In a cold year allow a week or two more.