When to plant cucumbers in Leuven: 31 May – 7 September

In Leuven, cucumber: sow for seedlings from 12 April to 10 August; plant into a greenhouse from 10 May to 7 September; plant out into open ground from 31 May to 7 September. For plants and seeds, the places nearby include Aveve (garden centre, 12 km) and Boomkwekerij Asselberghs (garden centre, 13 km); addresses and opening hours are below.

Cucumber in Leuven: soil, season and weather

In Leuven the soil, not frost, sets the date: the last frost is over around 19 April, but the top 7 cm of soil reaches 18 °C — the minimum on the cucumber card — only around 31 May, 42 days later.

Last spring frost	19 April
Top 7 cm of soil at 18 °C	31 May, 42 days after the last frost
Into an unheated greenhouse	10 May – 7 September; May outside: 8.8 °C at night, 19.1 °C by day; card 18–25 °C
First autumn frost	22 November, 175 days after the start
Days in the bed to the first harvest (card)	34
First harvest, if planted in this window	4 July – 11 October
Days left for picking	141
Daylight	14:52 on 3 May, 16:10 on 31 May
Watering outdoors when fruiting (card)	every 2 days; the driest month, September, has 11 rainy days

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

Cucumber in Leuven: care after planting

Planted on 31 May: in the first weeks water every 4 days.

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

7 June — 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 Leuven during the cucumber season

No month of the season averages above the cucumber card's 18–35 °C by day; the warmest, August, averages 23.7 °C. Months that stay below 18 °C even by day on average: October (15.9 °C) and November (10.2 °C). Nights average below 18 °C in every month of the season, from 4.7 °C to 14.3 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	19.1	8.8	69	11	15:30
June	22.7	13.1	81	12	16:30
July	23.5	14	79	12	16:06
August	23.7	14.3	69	13	14:36
September	20.6	11.8	62	11	12:42
October	15.9	9.3	81	13	10:47
November	10.2	4.7	70	14	8:59

ERA5 2016–2025, Open-Meteo

Cucumber in nearby cities

Around Leuven, Hasselt is 1 day earlier and Namur 11 days later.

City	Distance	Date	Difference
Brussels	25 km	8 June – 7 September	8 days later
Antwerp	43 km	31 May – 7 September	same day
Hasselt	45 km	30 May – 3 September	1 day earlier
Namur	47 km	11 June – 31 August	11 days later
Charleroi	55 km	10 June – 31 August	10 days later
Liège	67 km	4 June – 4 September	4 days later

Where to buy cucumber plants and seeds near Leuven

Buy plants ready to set out from 31 May to 7 September (from 10 May to 7 September for an unheated greenhouse); seed for raising your own is sown from 12 April to 10 August. Within 15 km of Leuven OpenStreetMap lists 31 garden centres, 1 plant nursery, 7 markets and 21 farm shops (collected 27 October 2026).

Aveve — garden centre
Mulslaan 17, 1820 Steenokkerzeel · Mon–Sat 09:00–18:00 · 14 km · aveve.be
Aveve — garden centre
Mechelsesteenweg 32 · Mon–Sat 09:00–18:00 · 12 km · aveve.be
Boomkwekerij Asselberghs — garden centre
Jennekensstraat 2, 3200 Aarschot · 13 km · boomkwekerij-asselberghs.be
Aveve — garden centre
Monnikstraat 26, 3128 Baal · 14 km · aveve.be

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.

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