Cornflower · Geoje, Gyeongsangnam-do, South Korea
When to sow cornflowers in Geoje
Main outdoor window
18 Feb - 18 Mar
The window this page is built around.
Timed from last spring frost
11 March
In Geoje, on your chosen risk.
Ready to pick
24 Apr - 14 May
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 Geoje
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.
Start indoors
28 Jan - 25 Feb
Six weeks before your last frost, under cover or on a windowsill.
Sow direct
18 Feb - 18 Mar
Three weeks before your last frost.
Plant out
25 Feb - 25 Mar
Two weeks before your last frost.
In flower
24 Apr - 14 May
Cornflowers through the year
Against the frost risk in Geoje
Why these dates
Sow direct three weeks before the last frost, thinly and where it is to flower - it resents transplanting once the taproot is down. Deadhead relentlessly, because a plant allowed to set seed stops flowering within a fortnight. An autumn sowing gives much taller, sturdier plants.
Hardy to about -10C as a young plant, which is what makes autumn sowing possible in zone 7 and milder. Dislikes humid heat and finishes early in a hot summer.
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. Cornflowers are timed from 6 weeks before that frost for an indoor start, with planting out 2 weeks before it, and this page simply resolves those offsets against the frost date computed for Geoje.
Hardiness is not the obstacle here. Geoje is zone 8b, comfortably inside the range this crop is rated for, so an established plant should come through an average winter without protection.
The median frost-free season here is 267 days, against 65 to 85 days to first flower for this crop counted from sowing. That margin is what decides whether a late sowing is worth attempting.
Also in Geoje
Other flowers to time
Growing cornflowers in Geoje
When should I plant cornflowers in Geoje?
Aim for 18 Feb - 18 Mar in an average year. If you would rather not gamble on the weather, wait until 4 Mar - 1 Apr - by then frost has finished in nine years out of ten.
When will cornflowers be ready to harvest in Geoje?
Expect to start picking around 24 Apr - 14 May, based on 65 to 85 days to maturity from the planting date calculated for this location.
How much frost will cornflowers tolerate?
Hardy to about -10C as a young plant, which is what makes autumn sowing possible in zone 7 and milder. Dislikes humid heat and finishes early in a hot summer.