When to plant watermelons in Sion: 28 June – 10 July

In Sion, watermelon: sow for seedlings from 10 May to 12 June; plant into a greenhouse from 7 June to 10 July; plant out into open ground from 28 June to 10 July. For plants and seeds, the places nearby include Ferme Vuissoz (farm shop, 2 km) and Point Vert (garden centre, 5 km); addresses and opening hours are below.

Watermelon in Sion: soil, season and weather

In Sion the soil, not frost, sets the date: the last frost is over around 8 May, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 28 June, 51 days later. 113 days separate planting out (28 June) from the first autumn frost (19 October); the card's 59 days to the first harvest leave 54 for picking, so a start 7 weeks late would still fit.

Last spring frost	8 May
Top 7 cm of soil at 18 °C	28 June, 51 days after the last frost
Into an unheated greenhouse	7 June – 10 July; June outside: 9.5 °C at night, 20.2 °C by day; card 18–35 °C
First autumn frost	19 October, 113 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	26 August – 7 September
Days left for picking	54
Daylight	15:30 on 31 May, 15:46 on 28 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, September, has 12 rainy days

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

Watermelon in Sion: care after planting

Planted on 28 June: in the first weeks water every 5 days.

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

28 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 Sion during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 22 °C. Months that stay below 18 °C even by day on average: September (17.7 °C) and October (13.7 °C). Nights average below 18 °C in every month of the season, from 2.9 °C to 11.1 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	20.2	9.5	125	18	15:46
July	21.8	11.1	115	16	15:27
August	22	10.8	103	14	14:12
September	17.7	7.1	91	12	12:36
October	13.7	2.9	105	12	10:59

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Sion, Neuchâtel is 22 days earlier and Aosta 3 days later.

City	Distance	Date	Difference
Aosta	55 km	1 July – 13 July	3 days later
Lausanne	65 km	19 June – 11 August	9 days earlier
Fribourg	65 km	21 June – 28 July	7 days earlier
Bern	80 km	21 June – 25 July	7 days earlier
Neuchâtel	91 km	6 June – 19 August	22 days earlier
Geneva	94 km	8 June – 8 August	20 days earlier

Where to buy watermelon plants and seeds near Sion

Buy plants ready to set out from 28 June to 10 July (from 7 June to 10 July for an unheated greenhouse); seed for raising your own is sown from 10 May to 12 June. Within 15 km of Sion OpenStreetMap lists 4 garden centres, 1 farm-supply shop, 1 plant nursery, 1 market and 4 farm shops (collected 27 October 2026).

Point Vert — garden centre
Mon–Thu 08:00–18:30; Sat 08:00–17:00; Fri 08:00–20:00 · 5 km
Marché de la vieille ville — market
Fri 08:00–14:00 · 0 km · mvvsion.ch
Ferme Vuissoz — farm shop
Chemin de Maragnène 40, 1950 · 2 km · ferme-vuissoz.ch
Self-Service Bio — farm shop
Feb 15–Dec 31 Mon–Sat 10:00–19:00 · 14 km · reynard-biotop.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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