Sweetcorn · Minato City, Tokyo, Japan
When to plant sweetcorn in Minato City
Main outdoor window
15-29 Mar
The window this page is built around.
Timed from last spring frost
8 March
In Minato City, on your chosen risk.
Ready to pick
14 May - 23 Jun
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 Minato City
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.
Sow direct
15-29 Mar
One week after your last frost.
Harvest
14 May - 23 Jun
Sweetcorn through the year
Against the frost risk in Minato City
Why these dates
Seed rots in cold wet soil. Sowing a week after last frost into 15C soil beats sowing on the frost date into 10C soil almost every time.
Seedlings survive a very light frost if the growing point is still below soil level, but growth stalls. Mature plants are killed outright.
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. Sweetcorn are timed for direct sowing 1 weeks after it, and this page simply resolves those offsets against the frost date computed for Minato City.
The median frost-free season here is 291 days, against 60 to 100 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Minato City
Other vegetables to time
Growing sweetcorn in Minato City
When should I plant sweetcorn in Minato City?
Aim for 15-29 Mar in an average year. If you would rather not gamble on the weather, wait until 3-17 Apr - by then frost has finished in nine years out of ten.
When will sweetcorn be ready to harvest in Minato City?
Expect to start picking around 14 May - 23 Jun, based on 60 to 100 days to maturity from the planting date calculated for this location.
How much frost will sweetcorn tolerate?
Seedlings survive a very light frost if the growing point is still below soil level, but growth stalls. Mature plants are killed outright.