Oca · Shanghai, Shanghai, China
When to plant oca in Shanghai
Main outdoor window
2-30 Mar
The window this page is built around.
Timed from last spring frost
2 March
In Shanghai, 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 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.
Plant tubers
2-30 Mar
Around your last frost.
Harvest
1 Nov - 31 Dec
Oca through the year
Against the frost risk in Shanghai
Why these dates
Plant tubers after the last frost. Do not lift until several weeks after the tops are frosted - almost all the crop forms in that final window, and digging early gets nothing.
Foliage is killed around -2C, but tuber formation happens in the weeks just before and after that. In short-season climates a fleece over the plants buys the time the crop needs.
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. Oca are timed with planting out 0 weeks after it, and this page simply resolves those offsets against the frost date computed for Shanghai.
Hardiness is not the obstacle here. Shanghai 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 287 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 Shanghai
Other vegetables to time
Growing oca in Shanghai
When should I plant oca in Shanghai?
Aim for 2-30 Mar in an average year. If you would rather not gamble on the weather, wait until 14 Mar - 11 Apr - by then frost has finished in nine years out of ten.
When will oca be ready to harvest in Shanghai?
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 oca tolerate?
Foliage is killed around -2C, but tuber formation happens in the weeks just before and after that. In short-season climates a fleece over the plants buys the time the crop needs.