Shiso · Seongnam-si, Gyeonggi-do, South Korea
When to plant shiso in Seongnam-si
Main outdoor window
10 Apr - 1 May
The window this page is built around.
Timed from last spring frost
3 April
In Seongnam-si, on your chosen risk.
Ready to pick
26 Jun - 16 Jul
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 Seongnam-si
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
20 Feb - 13 Mar
Six weeks before your last frost, under cover or on a windowsill.
Sow direct
10 Apr - 1 May
One week after your last frost.
Plant out
17 Apr - 8 May
Two weeks after your last frost.
Harvest
26 Jun - 16 Jul
Shiso through the year
Against the frost risk in Seongnam-si
Why these dates
Killed by the first frost, like basil.
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. Shiso are timed from 6 weeks before that frost for an indoor start, with planting out 2 weeks after it, and this page simply resolves those offsets against the frost date computed for Seongnam-si.
The median frost-free season here is 223 days, against 70 to 90 days to maturity for this crop counted from planting out. That margin is what decides whether a late sowing is worth attempting.
Growing shiso in Seongnam-si
When should I plant shiso in Seongnam-si?
Aim for 10 Apr - 1 May in an average year. If you would rather not gamble on the weather, wait until 19 Apr - 10 May - by then frost has finished in nine years out of ten.
When will shiso be ready to harvest in Seongnam-si?
Expect to start picking around 26 Jun - 16 Jul, based on 70 to 90 days to maturity from the planting date calculated for this location.
How much frost will shiso tolerate?
Killed by the first frost, like basil.