Iceberg lettuce · Xuhui, Shanghai, China
When to plant iceberg lettuce in Xuhui
Main outdoor window
9-23 Feb
The window this page is built around.
Timed from last spring frost
2 March
In Xuhui, on your chosen risk.
Ready to pick
1 Jun - 30 Sep
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 Xuhui
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.
Start indoors
19 Jan - 2 Feb
Six weeks before your last frost, under cover or on a windowsill.
Sow direct
9-23 Feb
Three weeks before your last frost.
Transplant
16 Feb - 2 Mar
Two weeks before your last frost.
Harvest
1 Jun - 30 Sep
Iceberg lettuce through the year
Against the frost risk in Xuhui
Why these dates
Start indoors six weeks before the last frost and plant out two weeks before. A check to growth at any point gives you a loose head rather than a dense one.
Takes around -3C. The long season means a late sowing can be caught by the first autumn frost before it has hearted.
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. Iceberg lettuce are timed from 6 weeks before that frost for an indoor start, with planting out 2 weeks before it, and this page simply resolves those offsets against the frost date computed for Xuhui.
The median frost-free season here is 287 days, against 70 to 85 days to maturity for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Xuhui
Other vegetables to time
Growing iceberg lettuce in Xuhui
When should I plant iceberg lettuce in Xuhui?
Aim for 9-23 Feb in an average year. If you would rather not gamble on the weather, wait until 21 Feb - 7 Mar - by then frost has finished in nine years out of ten.
When will iceberg lettuce be ready to harvest in Xuhui?
Expect to start picking around 1 Jun - 30 Sep, based on 70 to 85 days to maturity from the planting date calculated for this location.
How much frost will iceberg lettuce tolerate?
Takes around -3C. The long season means a late sowing can be caught by the first autumn frost before it has hearted.