GreenlyWhen to plant tomato in Denver
In Denver, tomato: sow seedlings around 19 February for the greenhouse and around 12 March for open ground; plant into a greenhouse around 17 April; plant out into open ground around 8 May.
Last spring frost around 1 May, first autumn frost around 15 October. Frost-free days: 167 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.