When to plant watermelons in Basel: 5 June – 11 August

In Basel, watermelon: sow for seedlings from 17 April to 14 July; plant into a greenhouse from 15 May to 11 August; plant out into open ground from 5 June to 11 August.

Watermelon in Basel: soil, season and weather

In Basel the soil, not frost, sets the date: the last frost is over around 5 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 5 June, 61 days later.

Last spring frost	5 April
Top 7 cm of soil at 18 °C	5 June, 61 days after the last frost
Into an unheated greenhouse	15 May – 11 August; May outside: 9.5 °C at night, 18.6 °C by day; card 18–35 °C
First autumn frost	20 November, 168 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	3 August – 9 October
Days left for picking	109
Daylight	14:47 on 8 May, 15:48 on 5 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, September, has 12 rainy days

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

Watermelon in Basel: care after planting

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

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

5 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 Basel during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 25.6 °C. Months that stay below 18 °C even by day on average: October (16.6 °C) and November (10 °C). Nights average below 18 °C in every month of the season, from 3.5 °C to 15.8 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	24	14.5	118	16	15:57
July	25.4	15.8	108	14	15:37
August	25.6	15.8	95	12	14:19
September	21.2	12.2	86	12	12:38
October	16.6	8.5	100	12	10:56
November	10	3.5	107	16	9:20

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Basel, Mulhouse is 4 days earlier and Lucerne 23 days later.

City	Distance	Date	Difference
Mulhouse	29 km	1 June – 8 August	4 days earlier
Freiburg im Breisgau	52 km	4 June – 7 August	1 day earlier
Colmar	60 km	16 June – 8 August	11 days later
Bern	69 km	21 June – 25 July	16 days later
Zurich	74 km	11 June – 7 August	6 days later
Lucerne	79 km	28 June – 11 July	23 days later

Where to buy watermelon plants and seeds near Basel

Buy plants ready to set out from 5 June to 11 August (from 15 May to 11 August for an unheated greenhouse); seed for raising your own is sown from 17 April to 14 July. Within 15 km of Basel OpenStreetMap lists 16 garden centres, 2 farm-supply shops, 2 plant nurseries, 18 markets and 125 farm shops (collected 27 October 2026).

Wochennmarkt Reinach — market
Hauptstrasse 10, 4153 Reinach BL · Apr–Oct Fri 07:30–11:30, Nov–Mar Fri 08:30–11:30 · 7 km
Bio Wochenmarkt Ettingen — market
Hauptstrasse 66, 4107 Ettingen · Sat 09:00–12:00 · 10 km
Bauernmarkt Liestal — market
Zeughausplatz 26, 4410 Liestal · Tue 08:00–14:00 · 14 km
Basler Stadtmarkt — market
Tue–Thu 08:00–14:00; Fri–Sat 08:00–17:00 · 0 km · bs.ch

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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