When to plant tomatoes in Portsmouth: 21 May – 11 August

In Portsmouth, tomato: sow for seedlings from 9 March to 20 June; plant into a greenhouse from 30 April to 11 August; plant out into open ground from 21 May to 11 August. For plants and seeds, the places nearby include Alver Valley (garden centre, 6 km) and Abbey Garden Centre (garden centre, 11 km); addresses and opening hours are below.

Tomato in Portsmouth: soil, season and weather

In Portsmouth the soil, not frost, sets the date: the last frost is over around 4 March, but the top 7 cm of soil reaches 15 °C — the minimum on the tomato card — only around 21 May, 78 days later.

Last spring frost	4 March
Top 7 cm of soil at 15 °C	21 May, 78 days after the last frost
Into an unheated greenhouse	30 April – 11 August; April outside: 6.1 °C at night, 12.8 °C by day; card 16–27 °C
First autumn frost	1 December, 194 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	30 July – 20 October
Days left for picking	124
Daylight	12:47 on 30 March, 15:46 on 21 May
Watering outdoors when fruiting (card)	every 3 days; the driest month, May, has 11 rainy days

Tomato in Portsmouth: care after planting

Planted on 21 May: in the first weeks water every 4 days.

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

21 May — feed: balanced (NPK)
18 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 Portsmouth during the tomato season

No month of the season averages above the tomato card's 16–27 °C by day; the warmest, July, averages 20.7 °C. Months that stay below 16 °C even by day on average: October (15.5 °C), November (11.7 °C) and December (9.7 °C). Nights average below 16 °C in every month of the season, from 5.6 °C to 14.9 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	16.1	9.4	51	11	15:30
June	19	12.8	59	11	16:29
July	20.7	14.9	60	12	16:05
August	20.7	14.8	64	11	14:36
September	18.9	13	79	11	12:42
October	15.5	10.8	108	14	10:47
November	11.7	7.1	100	14	8:59
December	9.7	5.6	98	14	7:59

ERA5 2016–2025, Open-Meteo

Tomato in nearby cities

All the nearest cities on our list plant tomato later than Portsmouth; the closest date is in Southampton, 2 days later.

City	Distance	Date	Difference
Southampton	24 km	23 May – 3 August	2 days later
Brighton	67 km	18 June – 11 August	28 days later
London	103 km	24 May – 3 August	3 days later
Oxford	105 km	26 May – 3 August	5 days later
Bristol	127 km	28 May – 2 August	7 days later
Cardiff	164 km	26 May – 2 August	5 days later

Where to buy tomato plants and seeds near Portsmouth

Buy plants ready to set out from 21 May to 11 August (from 30 April to 11 August for an unheated greenhouse); seed for raising your own is sown from 9 March to 20 June. Within 15 km of Portsmouth OpenStreetMap lists 16 garden centres, 4 plant nurseries, 5 markets and 8 farm shops (collected 28 October 2026).

Alver Valley — garden centre
Barrington Close, PO13 8NZ Gosport · Mon–Sat 09:00–17:30; Sun 10:30–16:30 · 6 km · yourlocalgardencentre.co.uk
Abbey Garden Centre — garden centre
Mill Lane, PO15 5RB · 11 km · abbeygardencentre.co.uk
Garsons — garden centre
Fontley Road, PO15 6QX Fareham · 12 km · garsons.co.uk
Stansted Park Garden Centre — garden centre
Rowlands Castle, PO9 6DX Stansted · 15 km · stanstedparkgardencentre.co.uk

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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