Watermelon · Shanghai, Shanghai, China
When to plant watermelons in Shanghai
Main outdoor window
16 Mar - 6 Apr
The window this page is built around.
Timed from last spring frost
2 March
In Shanghai, on your chosen risk.
Ready to pick
1 Aug - 30 Sep
If you plant at the start of the window.
The average last frost. Half of all years are later than this.
Step by step in Shanghai
Each window is a range, not a single day. Earlier in the range buys you a longer season; later in it buys you a safer one.
Start indoors
26 Jan - 16 Feb
Five weeks before your last frost, under cover or on a windowsill.
Plant out
16 Mar - 6 Apr
Two weeks after your last frost.
Harvest
1 Aug - 30 Sep
Watermelons through the year
Against the frost risk in Shanghai
Why these dates
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.
Killed at 0C, and checked hard by anything below 12C. Frost dates matter less here than the run of warm nights between them.
Seed packets and extension guides express timing as weeks either side of the last spring frost, because that is the only reference point that travels. Watermelons are timed from 5 weeks before that frost for an indoor start, with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for Shanghai.
The median frost-free season here is 287 days, against 80 to 110 days to maturity for this crop counted from planting out. That margin is what decides whether a late sowing is worth attempting.
Also in Shanghai
Other vegetables to time
Growing watermelons in Shanghai
When should I plant watermelons in Shanghai?
Aim for 16 Mar - 6 Apr in an average year. If you would rather not gamble on the weather, wait until 28 Mar - 18 Apr - by then frost has finished in nine years out of ten.
When will watermelons be ready to harvest in Shanghai?
Expect to start picking around 1 Aug - 30 Sep, based on 80 to 110 days to maturity from the planting date calculated for this location.
How much frost will watermelons tolerate?
Killed at 0C, and checked hard by anything below 12C. Frost dates matter less here than the run of warm nights between them.