Water chestnut · Tokyo, Tokyo, Japan
When to plant water chestnuts in Tokyo
Main outdoor window
22 Mar - 12 Apr
The window this page is built around.
Timed from last spring frost
8 March
In Tokyo, on your chosen risk.
Ready to pick
1 Oct - 31 Dec
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 Tokyo
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.
Plant corms
22 Mar - 12 Apr
Two weeks after your last frost.
Harvest
1 Oct - 31 Dec
Water chestnuts through the year
Against the frost risk in Tokyo
Why these dates
Plant corms two weeks after the last frost into 5cm of standing water. Drain in autumn once the tops yellow, then dig the corms out of the drying mud.
Top growth is killed at 0C, which is the signal to drain and harvest. Corms need around 200 frost-free days to size up.
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. Water chestnuts are timed with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for Tokyo.
The median frost-free season here is 291 days, against 180 to 220 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Tokyo
Other vegetables to time
Growing water chestnuts in Tokyo
When should I plant water chestnuts in Tokyo?
Aim for 22 Mar - 12 Apr in an average year. If you would rather not gamble on the weather, wait until 10 Apr - 1 May - by then frost has finished in nine years out of ten.
When will water chestnuts be ready to harvest in Tokyo?
Expect to start picking around 1 Oct - 31 Dec, based on 180 to 220 days to maturity from the planting date calculated for this location.
How much frost will water chestnuts tolerate?
Top growth is killed at 0C, which is the signal to drain and harvest. Corms need around 200 frost-free days to size up.