GreenlyWhen to plant tomato in Seattle
In Seattle, tomato: sow seedlings around 28 February for the greenhouse and around 21 March for open ground; plant into a greenhouse around 26 April; plant out into open ground around 17 May.
Last spring frost around 20 March, first autumn frost around 24 November. Frost-free days: 249 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.