Sunflower · Hyesan, Yanggang-do, North Korea
When to sow sunflowers in Hyesan
Main outdoor window
22 May - 5 Jun
The window this page is built around.
Timed from last spring frost
15 May
In Hyesan, on your chosen risk.
Ready to pick
31 Jul - 30 Aug
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 Hyesan
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.
Sow direct
22 May - 5 Jun
One week after your last frost.
In flower
31 Jul - 30 Aug
Sunflowers through the year
Against the frost risk in Hyesan
Why these dates
Sow a short row every two weeks until ten weeks before first frost for continuous cut flowers rather than one brief spectacle.
Seedlings are killed by frost. Once flowering, stems tolerate a light autumn frost without damage.
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. Sunflowers are timed for direct sowing 1 weeks after it, and this page simply resolves those offsets against the frost date computed for Hyesan.
The median frost-free season here is 137 days, against 70 to 100 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Growing sunflowers in Hyesan
When should I plant sunflowers in Hyesan?
Aim for 22 May - 5 Jun in an average year. If you would rather not gamble on the weather, wait until 3-17 Jun - by then frost has finished in nine years out of ten.
When will sunflowers be ready to harvest in Hyesan?
Expect to start picking around 31 Jul - 30 Aug, based on 70 to 100 days to maturity from the planting date calculated for this location.
How much frost will sunflowers tolerate?
Seedlings are killed by frost. Once flowering, stems tolerate a light autumn frost without damage.