🧅 Onion
Leaves first, bulbs later — day length tells it when to finish.
Onion at a glance
Is Onion frost tolerant?
Yes — it is one of the hardier crops. It shrugs off frost down to -6°C and is only killed below -12°C.
What temperature does Onion grow best in?
It grows best between 8 and 28°C. Below 5°C it stops growing altogether, and above 31°C it slows down.
How many days does Onion take to mature?
About 90–110 days. That is a typical figure: it needs roughly 1050 °C·d of warmth above 5°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 Onion 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 31°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, 30) − 5), and Onion is ready when that total reaches 1050. That is why the same seed takes a very different number of days in Dublin and in Guangzhou.
| Base temperature | 5°CBelow this, the plant accumulates no growing degree days at all. |
|---|---|
| Degree days to maturity | 1050 °C·dThe heat budget it must accumulate before it is ready to pick. |
| Comfortable range | 8–28°CWhere it grows without stress. |
| Frost damage below | -6°CLeaves start taking frost damage below this low. |
| Killed below | -12°CBelow this it does not come back. |
| Heat stress above | 31°CAbove this the plant slows down and stops setting fruit well. |
| Typical time to harvest | 90–110 days |
| Yield per bed | 10 onions |
Things worth knowing
- Onion varieties are classed by day length — a long-day onion near the equator grows leaves forever.
- Chopping onions releases a tear-inducing compound; chill them first and you'll cry much less.
Where and when to sow Onion
Pick your city to see the months when Onion scores well against that city's real climate records: