🥗 Lettuce
Loves cool, moist weather — crisp and tender in mild climates.
Lettuce at a glance
Is Lettuce frost tolerant?
Yes, through light frosts. Damage starts at -3°C and it is killed below -8°C.
What temperature does Lettuce grow best in?
It grows best between 7 and 24°C. Below 4°C it stops growing altogether, and above 26°C it slows down.
How many days does Lettuce take to mature?
About 50–70 days. That is a typical figure: it needs roughly 650 °C·d of warmth above 4°C, so a warm season gets it there sooner and a cool one later. The city calendars below give the sow and harvest dates for each place.
Is Lettuce a cool-season or warm-season crop?
A cool-season crop. It does best in the mild weather of spring and autumn, and slows down in summer heat above 26°C.
What the numbers mean
These are the actual parameters this game runs on. Growth is driven by growing degree days: each day contributes max(0, min(mean temp, 28) − 4), and Lettuce is ready when that total reaches 650. That is why the same seed takes a very different number of days in Dublin and in Guangzhou.
| Base temperature | 4°CBelow this, the plant accumulates no growing degree days at all. |
|---|---|
| Degree days to maturity | 650 °C·dThe heat budget it must accumulate before it is ready to pick. |
| Comfortable range | 7–24°CWhere it grows without stress. |
| Frost damage below | -3°CLeaves start taking frost damage below this low. |
| Killed below | -8°CBelow this it does not come back. |
| Heat stress above | 26°CAbove this the plant slows down and stops setting fruit well. |
| Typical time to harvest | 50–70 days |
| Yield per bed | 6 heads |
Things worth knowing
- The milky sap contains lactucarium; ancient Romans ate lettuce before bed to sleep better.
- Above 24°C lettuce bolts to flower and the leaves turn bitter.
Where and when to sow Lettuce
Pick your city to see the months when Lettuce scores well against that city's real climate records: