When to plant watermelons in Siena: 26 May – 18 August

In Siena, watermelon: sow for seedlings from 7 April to 21 July; plant into a greenhouse from 5 May to 18 August; plant out into open ground from 26 May to 18 August.

Watermelon in Siena: soil, season and weather

In Siena the soil, not frost, sets the date: the last frost is over around 16 March, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 26 May, 71 days later.

Last spring frost	16 March
Top 7 cm of soil at 18 °C	26 May, 71 days after the last frost
Into an unheated greenhouse	5 May – 18 August; May outside: 11 °C at night, 22.5 °C by day; card 18–35 °C
First autumn frost	27 November, 185 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	24 July – 16 October
Days left for picking	126
Daylight	13:59 on 28 April, 15:01 on 26 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 4 rainy days

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

Watermelon in Siena: care after planting

Planted on 26 May: in the first weeks water every 5 days.

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

26 May — 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 Siena during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 32.5 °C. Months that stay below 18 °C even by day on average: November (15.2 °C). Nights average below 18 °C in May, June and September–November (6.2–16 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	22.5	11	91	12	14:40
June	29.1	16	41	7	15:23
July	32.5	18.8	22	4	15:06
August	32.4	18.9	35	6	14:00
September	26.5	14.8	77	8	12:33
October	21.4	10.9	97	8	11:05
November	15.2	6.2	107	12	9:44

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Siena, Livorno is 10 days earlier and Pisa 21 days later.

City	Distance	Date	Difference
Arezzo	47 km	9 June – 12 August	14 days later
Florence	50 km	28 May – 18 August	2 days later
Livorno	84 km	from 16 May	10 days earlier
Pisa	87 km	16 June – 9 August	21 days later
Perugia	89 km	29 May – 16 August	3 days later
San Marino	113 km	16 May – 2 September	10 days earlier

Where to buy watermelon plants and seeds near Siena

Buy plants ready to set out from 26 May to 18 August (from 5 May to 18 August for an unheated greenhouse); seed for raising your own is sown from 7 April to 21 July. Within 15 km of Siena OpenStreetMap lists 3 garden centres, 2 farm-supply shops, 4 plant nurseries, 6 markets and 1 farm shop (collected 27 October 2026).

Mercato del Petriccio — market
Piazza Enrico Lachi, 53100 Siena · Mon 06:30–14:00 · 3 km
Mercato di San Miniato — market
Piazza Pertini, 53100 Siena · Sat 07:00–14:00 · 3 km
Mercato di Taverne d'Arbia — market
Piazza Montaperti, 53100 · Tue, Thu 07:00–14:30 · 6 km
Mercato della Tognazza — market
Via Franco Ferrini, Siena · 5 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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