When to plant tomatoes in Letterkenny: 7 June – 8 August

In Letterkenny, tomato: sow for seedlings from 26 March to 17 June; plant into a greenhouse from 17 May to 8 August; plant out into open ground from 7 June to 8 August. For plants and seeds, the places nearby include Gary's Petworld and Garden Centre (garden centre, 2 km); addresses and opening hours are below.

Tomato in Letterkenny: soil, season and weather

In Letterkenny the soil, not frost, sets the date: the last frost is over around 30 March, but the top 7 cm of soil reaches 15 °C — the minimum on the tomato card — only around 7 June, 69 days later.

Last spring frost	30 March
Top 7 cm of soil at 15 °C	7 June, 69 days after the last frost
Into an unheated greenhouse	17 May – 8 August; May outside: 7.4 °C at night, 15 °C by day; card 16–27 °C
First autumn frost	28 November, 174 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	16 August – 17 October
Days left for picking	104
Daylight	14:09 on 16 April, 17:09 on 7 June
Watering outdoors when fruiting (card)	every 3 days; the driest month, September, has 18 rainy days

Tomato in Letterkenny: care after planting

Planted on 7 June: in the first weeks water every 4 days.

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

7 June — feed: balanced (NPK)
5 July — 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 Letterkenny during the tomato season

No month of the season averages above the tomato card's 16–27 °C by day; the warmest, August, averages 17.7 °C. Months that stay below 16 °C even by day on average: September (15.8 °C), October (12.8 °C) and November (9.5 °C). Nights average below 16 °C in every month of the season, from 4.9 °C to 11.5 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	16.8	10.1	105	17	17:20
July	17.6	11.4	115	18	16:50
August	17.7	11.5	126	20	15:01
September	15.8	9.8	102	18	12:48
October	12.8	7.9	120	18	10:35
November	9.5	4.9	103	18	8:27

ERA5 2016–2025, Open-Meteo

Tomato in nearby cities

Around Letterkenny, Athlone is 5 days earlier and Belfast 8 days later.

City	Distance	Date	Difference
Derry	26 km	7 June – 1 August	same day
Sligo	91 km	6 June – 1 August	1 day earlier
Belfast	122 km	15 June – 30 July	8 days later
Dundalk	137 km	14 June – 31 July	7 days later
Athlone	172 km	2 June – 6 August	5 days earlier
Dublin	203 km	12 June – 4 August	5 days later

Where to buy tomato plants and seeds near Letterkenny

Buy plants ready to set out from 7 June to 8 August (from 17 May to 8 August for an unheated greenhouse); seed for raising your own is sown from 26 March to 17 June. Within 15 km of Letterkenny OpenStreetMap lists 3 garden centres and 1 market (collected 28 October 2026).

Gary's Petworld and Garden Centre — garden centre
Mon–Fri 09:00–18:00 · 2 km
Alcorns — garden centre
2 km · alcorns.ie
Raphoe Garden Centre — garden centre
12 km
Market Square — market
2 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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