Mashua · Chōfu, Tokyo, Japan
When to plant mashua in Chōfu
Main outdoor window
1-29 Apr
The window this page is built around.
Timed from last spring frost
1 April
In Chōfu, on your chosen risk.
Ready to pick
1 Nov - 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 Chōfu
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 tubers
1-29 Apr
Around your last frost.
Harvest
1 Nov - 31 Dec
Mashua through the year
Against the frost risk in Chōfu
Why these dates
As for oca: the tops go at about -2C and the crop is lifted afterwards.
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. Mashua are timed with planting out 0 weeks after it, and this page simply resolves those offsets against the frost date computed for Chōfu.
Hardiness is not the obstacle here. Chōfu is zone 9a, comfortably inside the range this crop is rated for, so an established plant should come through an average winter without protection.
The median frost-free season here is 247 days, against 180 to 210 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Chōfu
Other vegetables to time
Growing mashua in Chōfu
When should I plant mashua in Chōfu?
Aim for 1-29 Apr in an average year. If you would rather not gamble on the weather, wait until 9 Apr - 7 May - by then frost has finished in nine years out of ten.
When will mashua be ready to harvest in Chōfu?
Expect to start picking around 1 Nov - 31 Dec, based on 180 to 210 days to maturity from the planting date calculated for this location.
How much frost will mashua tolerate?
As for oca: the tops go at about -2C and the crop is lifted afterwards.