When to plant watermelons in Bonn: 4 June – 10 August

In Bonn, watermelon: sow for seedlings from 16 April to 13 July; plant into a greenhouse from 14 May to 10 August; plant out into open ground from 4 June to 10 August.

Watermelon in Bonn: soil, season and weather

In Bonn the soil, not frost, sets the date: the last frost is over around 8 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 4 June, 57 days later.

Last spring frost	8 April
Top 7 cm of soil at 18 °C	4 June, 57 days after the last frost
Into an unheated greenhouse	14 May – 10 August; May outside: 8.9 °C at night, 19 °C by day; card 18–35 °C
First autumn frost	19 November, 168 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	2 August – 8 October
Days left for picking	109
Daylight	15:04 on 7 May, 16:16 on 4 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, August, has 12 rainy days

The same dates in Bonn hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in Bonn: care after planting

Planted on 4 June: in the first weeks water every 5 days.

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

4 June — feed: balanced (NPK)

Pests and diseases of watermelon 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 Bonn during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 24.8 °C. Months that stay below 18 °C even by day on average: October (15.9 °C) and November (10.1 °C). Nights average below 18 °C in every month of the season, from 4.3 °C to 14.9 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	23.6	13.6	76	12	16:28
July	24.3	14.6	83	13	16:05
August	24.8	14.9	64	12	14:35
September	21	11.8	77	10	12:41
October	15.9	8.9	70	14	10:48
November	10.1	4.3	73	15	9:00

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Bonn, Cologne is 1 day earlier and Dortmund 1 day later.

City	Distance	Date	Difference
Cologne	25 km	3 June – 11 August	1 day earlier
Düsseldorf	60 km	3 June – 12 August	1 day earlier
Duisburg	81 km	3 June – 13 August	1 day earlier
Essen	81 km	3 June – 12 August	1 day earlier
Bochum	84 km	3 June – 11 August	1 day earlier
Dortmund	90 km	5 June – 7 August	1 day later

Where to buy watermelon plants and seeds near Bonn

Buy plants ready to set out from 4 June to 10 August (from 14 May to 10 August for an unheated greenhouse); seed for raising your own is sown from 16 April to 13 July. Within 15 km of Bonn OpenStreetMap lists 32 garden centres, 4 farm-supply shops, 3 plant nurseries, 9 markets and 50 farm shops (collected 28 October 2026).

Rheinquartier Erzeugermarkt — market
Wed–Sat 10:00–19:00 · 14 km · rheinquartier.com
Wochenmarkt — market
Tue, Thu 08:00–13:00; Sat 08:00–14:00 · 6 km
Ökomarkt — market
Fri 08:00–14:00 · 6 km
Meckenheimer Wochenmarkt — market
Thu 07:30–13:00 · 13 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.

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