Vegetable · Cucurbitaceae
When to plant watermelons
The most heat-demanding thing in the vegetable garden. Below about 21C soil it simply sits there, and a cool summer gives you fruit with no sugar in it.
Start seed indoors
5 weeks before
Counted from your last spring frost.
Plant out
2 weeks after
Counted from your last spring frost.
Days to maturity
80-110
From planting out to a first picking.
Those weeks become real dates once you name a place.
Timing, in frost-relative terms
Seed packets rarely give calendar dates, because a date that suits one latitude is wrong at another. They give offsets from the last spring frost instead, and those offsets are what make watermelons plantable anywhere.
- Start seed indoors 5 weeks before the last frost.
- Plant out 2 weeks after the last frost.
- Expect 80–110 days to maturity, counted from planting out.
Getting the timing right
Start indoors five weeks before the last frost in pots that will not disturb the roots, and plant out two weeks after it under fleece or black plastic to lift soil temperature.
Frost tolerance
Killed at 0C, and checked hard by anything below 12C. Frost dates matter less here than the run of warm nights between them.
Classified as tender, with damage expected below 0°C (32°F)32°F (0°C).