When to plant tomatoes in Portland, Maine: 28 May – 15 July

In Portland, Maine, tomato: sow for seedlings from 16 March to 24 May; plant into a greenhouse from 7 May to 15 July; plant out into open ground from 28 May to 15 July. For plants and seeds, the places nearby include Allen Sterling & Lothrop (garden centre, 7 km) and Skillins Greenhouses (Trees) (garden centre, 7 km); addresses and opening hours are below.

Tomato in Portland, Maine: soil, season and weather

In Portland, Maine the soil, not frost, sets the date: the last frost is over around 15 April, but the top 7 cm of soil reaches 15 °C — the minimum on the tomato card — only around 28 May, 43 days later.

Last spring frost	15 April
Top 7 cm of soil at 15 °C	28 May, 43 days after the last frost
Into an unheated greenhouse	7 May – 15 July; May outside: 8.2 °C at night, 17.3 °C by day; card 16–27 °C
First autumn frost	4 November, 160 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	6 August – 23 September
Days left for picking	90
Daylight	12:58 on 6 April, 15:07 on 28 May
Watering outdoors when fruiting (card)	every 3 days; the driest month, September, has 9 rainy days

Tomato in Portland, Maine: care after planting

Planted on 28 May: in the first weeks water every 4 days.

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

28 May — feed: balanced (NPK)
25 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 Portland, Maine during the tomato season

No month of the season averages above the tomato card's 16–27 °C by day; the warmest, July, averages 26.1 °C. Months that stay below 16 °C even by day on average: October (15.6 °C) and November (8.4 °C). Nights average below 16 °C in May, June and September–November (1.2–13.9 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	17.3	8.2	82	10	14:42
June	22.6	13.9	85	11	15:25
July	26.1	17.9	95	11	15:08
August	25.3	17.2	83	10	14:01
September	21.7	13.7	80	9	12:33
October	15.6	8.1	121	10	11:05
November	8.4	1.2	95	9	9:42

ERA5 2016–2025, Open-Meteo

Tomato in nearby cities

Around Portland, Maine, Boston is 9 days earlier and Bangor 3 days later.

City	Distance	Date	Difference
Augusta	82 km	27 May – 14 July	1 day earlier
Concord	115 km	22 May – 11 July	6 days earlier
Manchester (United States)	122 km	20 May – 13 July	8 days earlier
Boston	159 km	19 May – 24 July	9 days earlier
Bangor	179 km	31 May – 14 July	3 days later
Montpelier	196 km	29 May – 27 June	1 day later

Where to buy tomato plants and seeds near Portland, Maine

Buy plants ready to set out from 28 May to 15 July (from 7 May to 15 July for an unheated greenhouse); seed for raising your own is sown from 16 March to 24 May. Within 15 km of Portland, Maine OpenStreetMap lists 5 garden centres, 6 markets and 1 farm shop (collected 20 October 2026).

Allen Sterling & Lothrop — garden centre
Route 1 191, 04105 Falmouth · 7 km
O'Days Nursery — garden centre
County Road 132, 04074 Scarborough · 12 km
Skillins Greenhouses (Trees) — garden centre
Mon–Fri 08:00–18:00; Sat 08:00–17:00; Sun 09:00–17:00 · 7 km
Skillens Greenhouses — garden centre
Mon–Fri 08:00–18:00; Sat 08:00–17:00; Sun 09:00–17:00 · 7 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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