When to plant cucumbers in Jeju City: 6 May – 4 October

In Jeju City, cucumber: sow for seedlings from 18 March to 6 September; plant into a greenhouse from 15 April to 4 October; plant out into open ground from 6 May to 4 October.

Cucumber in Jeju City: soil, season and weather

In Jeju City the soil, not frost, sets the date: the last frost is over around 18 February, but the top 7 cm of soil reaches 18 °C — the minimum on the cucumber card — only around 6 May, 77 days later.

Last spring frost	18 February
Top 7 cm of soil at 18 °C	6 May, 77 days after the last frost
Into an unheated greenhouse	15 April – 4 October; April outside: 11.4 °C at night, 17.6 °C by day; card 18–25 °C
First autumn frost	19 December, 227 days after the start
Days in the bed to the first harvest (card)	34
First harvest, if planted in this window	9 June – 7 November
Days left for picking	193
Daylight	12:46 on 8 April, 13:39 on 6 May
Watering outdoors when fruiting (card)	every 2 days; the driest month, December, has 14 rainy days

The same dates in Jeju City hold for Bell Pepper, Eggplant, Zucchini, Pumpkin and Watermelon.

Cucumber in Jeju City: care after planting

Planted on 6 May: in the first weeks water every 4 days.

Feeding, by the card’s schedule from that day:

13 May — feed: nitrogen

Pests and diseases of cucumber to watch for:

Dates count from the first planting day of the window above; a later planting moves them by as many days.

Weather in Jeju City during the cucumber season

No month of the season averages above the cucumber card's 18–35 °C by day; the warmest, August, averages 29.9 °C. Months that stay below 18 °C even by day on average: November (15.7 °C) and December (9.9 °C). Nights average below 18 °C in May and October–December (5.2–16.4 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	21.8	15.7	148	11	13:53
June	25	19.9	208	14	14:22
July	29	24.6	233	18	14:10
August	29.9	25.4	240	19	13:25
September	26.1	22	354	19	12:25
October	20.8	16.4	182	13	11:23
November	15.7	10.4	108	11	10:27
December	9.9	5.2	85	14	9:57

ERA5 2016–2025, Open-Meteo

Cucumber in nearby cities

All the nearest cities on our list plant cucumber later than Jeju City; the closest date is in Busan, 9 days later.

City	Distance	Date	Difference
Gwangju	187 km	17 May – 8 September	11 days later
Jeonju	263 km	19 May – 2 September	13 days later
Busan	299 km	15 May – 7 September	9 days later
Daegu	324 km	16 May – 6 September	10 days later
Daejeon	326 km	17 May – 28 August	11 days later
Ulsan	342 km	18 May – 1 September	12 days later

Where to buy cucumber plants and seeds near Jeju City

Buy plants ready to set out from 6 May to 4 October (from 15 April to 4 October for an unheated greenhouse); seed for raising your own is sown from 18 March to 6 September. Within 15 km of Jeju City OpenStreetMap lists 1 garden centre, 7 markets and 1 farm shop (collected 28 October 2026).

신오일장농수산물 — market
4 km
( Yusuamsangjeom ) — market
13 km
함덕오일시장 — market
14 km
화북종합시장 — market
5 km

Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.

Questions