🌻 Sunflower
The tallest thing in the garden all summer — heads over 30 cm across.
Sunflower at a glance
Is Sunflower frost tolerant?
Barely. A light frost is enough to damage it (0°C), and it is killed below -2°C. Treat it as frost-tender.
What temperature does Sunflower grow best in?
It grows best between 14 and 30°C. Below 8°C it stops growing altogether, and above 35°C it slows down.
How many days does Sunflower take to mature?
About 70–90 days. That is a typical figure: it needs roughly 1000 °C·d of warmth above 8°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 Sunflower a cool-season or warm-season crop?
Somewhere in between: it cannot take frost, so plant it after your last frost, but it starts growing from about 8°C — earlier in spring than the true heat-lovers.
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, 34) − 8), and Sunflower is ready when that total reaches 1000. That is why the same seed takes a very different number of days in Dublin and in Guangzhou.
| Base temperature | 8°CBelow this, the plant accumulates no growing degree days at all. |
|---|---|
| Degree days to maturity | 1000 °C·dThe heat budget it must accumulate before it is ready to pick. |
| Comfortable range | 14–30°CWhere it grows without stress. |
| Frost damage below | 0°CLeaves start taking frost damage below this low. |
| Killed below | -2°CBelow this it does not come back. |
| Heat stress above | 35°CAbove this the plant slows down and stops setting fruit well. |
| Typical time to harvest | 70–90 days |
| Yield per bed | 3 blooms |
Things worth knowing
- Only young sunflowers track the sun; mature heads face east — they warm up earlier and bees prefer them.
- One head is really a thousand tiny flowers; each outer "petal" is its own ray floret.
Where and when to sow Sunflower
Pick your city to see the months when Sunflower scores well against that city's real climate records: