When to plant tomatoes in Basel: 14 May – 31 July

In Basel, tomato: sow for seedlings from 2 March to 9 June; plant into a greenhouse from 23 April to 31 July; plant out into open ground from 14 May to 31 July. For plants and seeds, the places nearby include Villaverde (garden centre, 5 km) and Dehner (garden centre, 7 km); addresses and opening hours are below.

Tomato 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 15 °C — the minimum on the tomato card — only around 14 May, 39 days later.

Last spring frost	5 April
Top 7 cm of soil at 15 °C	14 May, 39 days after the last frost
Into an unheated greenhouse	23 April – 31 July; April outside: 5.5 °C at night, 15.2 °C by day; card 16–27 °C
First autumn frost	20 November, 190 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	23 July – 9 October
Days left for picking	120
Daylight	12:18 on 23 March, 15:04 on 14 May
Watering outdoors when fruiting (card)	every 3 days; the driest month, September, has 12 rainy days

Tomato in Basel: care after planting

Planted on 14 May: in the first weeks water every 4 days.

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

14 May — feed: balanced (NPK)
11 June — feed: nitrogen

Pests and diseases of tomato 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 tomato season

No month of the season averages above the tomato card's 16–27 °C by day; the warmest, August, averages 25.6 °C. Months that stay below 16 °C even by day on average: November (10 °C). Nights average below 16 °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
May	18.6	9.5	127	17	15:06
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

Tomato in nearby cities

Around Basel, Mulhouse is 1 day earlier and Lucerne 32 days later.

City	Distance	Date	Difference
Mulhouse	29 km	13 May – 28 July	1 day earlier
Freiburg im Breisgau	52 km	13 May – 27 July	1 day earlier
Colmar	60 km	31 May – 28 July	17 days later
Bern	69 km	3 June – 14 July	20 days later
Zurich	74 km	29 May – 27 July	15 days later
Lucerne	79 km	15 June – 30 June	32 days later

Where to buy tomato plants and seeds near Basel

Buy plants ready to set out from 14 May to 31 July (from 23 April to 31 July for an unheated greenhouse); seed for raising your own is sown from 2 March to 9 June. 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).

Dehner — garden centre
Rennemattenweg 14, 79576 Weil am Rhein · Mon–Fri 09:00–20:00; Sat 09:00–19:00 · 7 km · dehner.de
Blumen Schmitt — garden centre
Lörracher Straße 67, 79639 Grenzach-Wyhlen · Mon–Fri 08:30–18:30; Sat 08:30–16:00 · 7 km · blumen-schmitt.de
Hügel — garden centre
Mühlenstraße 1, 79595 Rümmingen · Mon–Sat 09:00–18:00; Sun, public holidays closed · 10 km · huegel-gartenbau.de
Villaverde — garden centre
Rue du Loup 34, 68220 Hésingue · 5 km · villaverde.fr

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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