Choy sum · Shuozhou, Shanxi, China
When to plant choy sum in Shuozhou
Main outdoor window
15-29 May
The window this page is built around.
Timed from last spring frost
8 May
In Shuozhou, 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 Shuozhou
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 May
One week after your last frost.
Harvest
1 Jun - 31 Oct
Choy sum through the year
Against the frost risk in Shuozhou
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 Shuozhou.
The median frost-free season here is 147 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 Shuozhou
Other vegetables to time
Growing choy sum in Shuozhou
When should I plant choy sum in Shuozhou?
Aim for 15-29 May in an average year. If you would rather not gamble on the weather, wait until 23 May - 6 Jun - by then frost has finished in nine years out of ten.
When will choy sum be ready to harvest in Shuozhou?
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.