🧅 Leek
The hardiest of the onion family — it can sit in frozen ground all winter and be lifted as needed.
Leek at a glance
Is Leek frost tolerant?
Yes — it is one of the hardier crops. It shrugs off frost down to -8°C and is only killed below -15°C.
What temperature does Leek grow best in?
It grows best between 7 and 24°C. Below 4°C it stops growing altogether, and above 28°C it slows down.
How many days does Leek take to mature?
About 100–130 days. That is a typical figure: it needs roughly 1150 °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 Leek a cool-season or warm-season crop?
A cool-season crop. It does best in the mild weather of spring and autumn (and through winter where winters are mild), and slows down in summer heat above 28°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 Leek is ready when that total reaches 1150. 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 | 1150 °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 | -8°CLeaves start taking frost damage below this low. |
| Killed below | -15°CBelow this it does not come back. |
| Heat stress above | 28°CAbove this the plant slows down and stops setting fruit well. |
| Typical time to harvest | 100–130 days |
| Yield per bed | 5 plants |
Things worth knowing
- The white shaft is made by earthing soil up around the stem; the part kept from the light stays pale and tender.
- The leek is the national plant of Wales, from a story of soldiers wearing one in their caps to tell friend from foe.
Where and when to sow Leek
Pick your city to see the months when Leek scores well against that city's real climate records: