When to plant watermelons in Plymouth: 17 July – 22 August

In Plymouth, watermelon: sow for seedlings from 29 May to 25 July; plant into a greenhouse from 26 June to 22 August; plant out into open ground from 17 July to 22 August.

Watermelon in Plymouth: soil, season and weather

In Plymouth the soil, not frost, sets the date: the last frost is over around 1 March, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 17 July, 138 days later.

Last spring frost	1 March
Top 7 cm of soil at 18 °C	17 July, 138 days after the last frost
Into an unheated greenhouse	26 June – 22 August; June outside: 13.6 °C at night, 16.1 °C by day; card 18–35 °C
First autumn frost	1 December, 137 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	14 September – 20 October
Days left for picking	78
Daylight	16:26 on 19 June, 15:57 on 17 July
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 9 rainy days

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

Watermelon in Plymouth: care after planting

Planted on 17 July: in the first weeks water every 5 days.

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

17 July — 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 Plymouth during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 18 °C. Months that stay below 18 °C even by day on average: July and September–December (11.2–17.9 °C). Nights average below 18 °C in every month of the season, from 8.8 °C to 15.7 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
July	17.9	15.3	54	9	16:01
August	18	15.7	64	10	14:33
September	17.1	14.5	93	13	12:41
October	15.1	12.7	140	16	10:49
November	12.6	10	141	17	9:02
December	11.2	8.8	138	18	8:03

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

All the nearest cities on our list plant watermelon earlier than Plymouth; the closest date is in Cardiff, 23 days earlier.

City	Distance	Date	Difference
Exeter	58 km	23 June – 18 August	24 days earlier
Swansea	140 km	21 June – 22 August	26 days earlier
Cardiff	141 km	24 June – 13 August	23 days earlier
Bristol	162 km	19 June – 13 August	28 days earlier
Southampton	202 km	17 June – 14 August	30 days earlier
Portsmouth	221 km	16 June – 22 August	31 days earlier

Where to buy watermelon plants and seeds near Plymouth

Buy plants ready to set out from 17 July to 22 August (from 26 June to 22 August for an unheated greenhouse); seed for raising your own is sown from 29 May to 25 July. Within 15 km of Plymouth OpenStreetMap lists 8 garden centres, 1 farm-supply shop, 5 markets and 2 farm shops (collected 20 October 2026).

Long Ash Garden Centre — garden centre
15 km
Ash Grosvenor — garden centre
5 km
Natural Source — farm supply
2 km
The Clipper — market
1 km · nudge.community

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.

Questions