Choy sum · Xinzhou, Shanxi, China
When to plant choy sum in Xinzhou
Main outdoor window
4-18 May
The window this page is built around.
Timed from last spring frost
27 April
In Xinzhou, 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 Xinzhou
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
4-18 May
One week after your last frost.
Harvest
1 Jun - 31 Oct
Choy sum through the year
Against the frost risk in Xinzhou
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 Xinzhou.
The median frost-free season here is 162 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 Xinzhou
Other vegetables to time
Growing choy sum in Xinzhou
When should I plant choy sum in Xinzhou?
Aim for 4-18 May in an average year. If you would rather not gamble on the weather, wait until 20 May - 3 Jun - by then frost has finished in nine years out of ten.
When will choy sum be ready to harvest in Xinzhou?
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.