When to plant tomatoes in Duluth: 5 June – 8 July

In Duluth, tomato: sow for seedlings from 24 March to 17 May; plant into a greenhouse from 15 May to 8 July; plant out into open ground from 5 June to 8 July. For plants and seeds, the places nearby include Growing Duluth (garden centre, 7 km); addresses and opening hours are below.

Tomato in Duluth: soil, season and weather

In Duluth the soil, not frost, sets the date: the last frost is over around 28 April, but the top 7 cm of soil reaches 15 °C — the minimum on the tomato card — only around 5 June, 38 days later.

Last spring frost	28 April
Top 7 cm of soil at 15 °C	5 June, 38 days after the last frost
Into an unheated greenhouse	15 May – 8 July; May outside: 6.6 °C at night, 15.9 °C by day; card 16–27 °C
First autumn frost	28 October, 145 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	14 August – 16 September
Days left for picking	75
Daylight	13:30 on 14 April, 15:41 on 5 June
Watering outdoors when fruiting (card)	every 3 days; the driest month, October, has 11 rainy days

Tomato in Duluth: care after planting

Planted on 5 June: in the first weeks water every 4 days.

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

5 June — feed: balanced (NPK)
3 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 Duluth during the tomato season

No month of the season averages above the tomato card's 16–27 °C by day; the warmest, July, averages 25.5 °C. Months that stay below 16 °C even by day on average: October (13.1 °C). Nights average below 16 °C in June (12.8 °C), September (14 °C) and October (7 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	21.9	12.8	87	11	15:50
July	25.5	17.3	85	10	15:31
August	24.4	17.2	88	10	14:15
September	21	14	90	10	12:37
October	13.1	7	72	11	10:58

ERA5 2016–2025, Open-Meteo

Tomato in nearby cities

Around Duluth, Madison is 20 days earlier and Thunder Bay 17 days later.

City	Distance	Date	Difference
Minneapolis	219 km	18 May – 4 July	18 days earlier
Thunder Bay	279 km	22 June – 3 July	17 days later
Fargo	356 km	18 May – 26 June	18 days earlier
Grand Forks	396 km	24 May – 26 June	12 days earlier
Green Bay	405 km	19 May – 10 July	17 days earlier
Madison	464 km	16 May – 7 July	20 days earlier

Where to buy tomato plants and seeds near Duluth

Buy plants ready to set out from 5 June to 8 July (from 15 May to 8 July for an unheated greenhouse); seed for raising your own is sown from 24 March to 17 May. Within 15 km of Duluth OpenStreetMap lists 1 garden centre and 1 market (collected 28 October 2026).

Growing Duluth — garden centre
Cody Street 6616, 55807 Duluth · 7 km · growingduluth.com
Farmer's Market — market
East 3rd Street 1324, 55805 Duluth · May–Oct: Wed 14:00–17:00, Sat 08:00–12:00; public holidays · 3 km · duluthfarmersmarket.com

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