Choy sum · Zhengzhou, Henan, China
When to plant choy sum in Zhengzhou
Main outdoor window
26 Mar - 9 Apr
The window this page is built around.
Timed from last spring frost
19 March
In Zhengzhou, on your chosen risk.
Ready to pick
1 Jun - 31 Oct
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 Zhengzhou
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
26 Mar - 9 Apr
One week after your last frost.
Harvest
1 Jun - 31 Oct
Choy sum through the year
Against the frost risk in Zhengzhou
Why these dates
Sow every two weeks from just after the last frost. Six weeks from seed to cutting means it slots into gaps between slower crops all season.
Damaged around -4C. Autumn sowings under cover crop well into early winter in mild climates.
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. Choy sum are timed for direct sowing 1 weeks after it, and this page simply resolves those offsets against the frost date computed for Zhengzhou.
The median frost-free season here is 243 days, against 40 to 55 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Zhengzhou
Other vegetables to time
Growing choy sum in Zhengzhou
When should I plant choy sum in Zhengzhou?
Aim for 26 Mar - 9 Apr in an average year. If you would rather not gamble on the weather, wait until 10-24 Apr - by then frost has finished in nine years out of ten.
When will choy sum be ready to harvest in Zhengzhou?
Expect to start picking around 1 Jun - 31 Oct, based on 40 to 55 days to maturity from the planting date calculated for this location.
How much frost will choy sum tolerate?
Damaged around -4C. Autumn sowings under cover crop well into early winter in mild climates.