GreenlyWhen to plant zucchini in Washington, D.C.
In Washington, D.C., zucchini: sow seedlings around 21 February for the greenhouse and around 14 March for open ground; plant into a greenhouse around 25 March; plant out into open ground around 15 April.
Last spring frost around 31 March, first autumn frost around 16 November. Frost-free days: 230 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.