When to plant tomatoes in Bismarck: 22 May – 25 June

In Bismarck, tomato: sow for seedlings from 10 March to 4 May; plant into a greenhouse from 1 May to 25 June; plant out into open ground from 22 May to 25 June.

Tomato in Bismarck: soil, season and weather

In Bismarck the soil, not frost, sets the date: the last frost is over around 1 May, but the top 7 cm of soil reaches 15 °C — the minimum on the tomato card — only around 22 May, 21 days later.

Last spring frost	1 May
Top 7 cm of soil at 15 °C	22 May, 21 days after the last frost
Into an unheated greenhouse	1 May – 25 June; May outside: 7.4 °C at night, 20.2 °C by day; card 16–27 °C
First autumn frost	15 October, 146 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	31 July – 3 September
Days left for picking	76
Daylight	12:44 on 31 March, 15:17 on 22 May
Watering outdoors when fruiting (card)	every 3 days; the driest month, October, has 5 rainy days

Tomato in Bismarck: care after planting

Planted on 22 May: in the first weeks water every 4 days.

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

22 May — feed: balanced (NPK)
19 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 Bismarck during the tomato season

Days average above the tomato card's 16–27 °C in July (29.1 °C) and August (27.6 °C). Months that stay below 16 °C even by day on average: October (13.7 °C). Nights average below 16 °C in May, June and August–October (3.6–15.8 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	20.2	7.4	67	10	15:01
June	26.6	14.1	69	9	15:51
July	29.1	17.2	63	8	15:31
August	27.6	15.8	68	8	14:15
September	23.4	11.8	55	7	12:37
October	13.7	3.6	44	5	10:58

ERA5 2016–2025, Open-Meteo

Tomato in nearby cities

Around Bismarck, Pierre is 13 days earlier and Grand Forks 2 days later.

City	Distance	Date	Difference
Pierre	274 km	9 May – 4 July	13 days earlier
Fargo	303 km	18 May – 26 June	4 days earlier
Grand Forks	303 km	24 May – 26 June	2 days later
Rapid City	360 km	20 May – 22 June	2 days earlier
Winnipeg	436 km	24 May – 22 June	2 days later
Sioux Falls	482 km	11 May – 1 July	11 days earlier

Where to buy tomato plants and seeds near Bismarck

Buy plants ready to set out from 22 May to 25 June (from 1 May to 25 June for an unheated greenhouse); seed for raising your own is sown from 10 March to 4 May. Within 15 km of Bismarck OpenStreetMap lists 1 garden centre and 1 market (collected 28 October 2026).

Bismarket — market
South Washington Street 318, 58504 Bismarck · Jun–Oct Sat 10:00–13:00 · 2 km · bismarket.com
Lowe's Plant Section — garden centre
4 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.

Questions