When to plant tomatoes in Flagstaff: 12 May – 1 July

In Flagstaff, tomato: sow for seedlings from 28 February to 10 May; plant into a greenhouse from 21 April to 1 July; plant out into open ground from 12 May to 1 July.

Tomato in Flagstaff: soil, season and weather

In Flagstaff frost, not soil, sets the date: the top 7 cm of soil warms to 15 °C — the minimum on the tomato card — around 19 April, 16 days before the last frost on 5 May, so planting waits only for the week after that frost.

Last spring frost	5 May
Top 7 cm of soil at 15 °C	19 April, 16 days before the last frost
Into an unheated greenhouse	21 April – 1 July; April outside: 3 °C at night, 17.4 °C by day; card 16–27 °C
First autumn frost	21 October, 162 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	21 July – 9 September
Days left for picking	92
Daylight	12:09 on 21 March, 13:55 on 12 May
Watering outdoors when fruiting (card)	every 3 days; the driest month, June, has 3 rainy days

The same dates in Flagstaff hold for Cucumber, Bell Pepper, Eggplant, Zucchini, Pumpkin and Watermelon.

Tomato in Flagstaff: care after planting

Planted on 12 May: in the first weeks water every 4 days.

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

12 May — feed: balanced (NPK)
9 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 Flagstaff during the tomato season

Days average above the tomato card's 16–27 °C in June (28.4 °C), July (29.7 °C) and August (27.8 °C). Nights average below 16 °C in May, June and August–October (6–15.3 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	21.4	7	23	6	14:00
June	28.4	13.7	15	3	14:31
July	29.7	16.5	53	10	14:19
August	27.8	15.3	51	10	13:30
September	24.7	12.1	27	5	12:26
October	18.4	6	24	4	11:20

ERA5 2016–2025, Open-Meteo

Tomato in nearby cities

All the nearest cities on our list plant tomato earlier than Flagstaff; the closest date is in Santa Fe (United States), 15 days earlier.

City	Distance	Date	Difference
Phoenix	197 km	11 February – 8 September	90 days earlier
Tucson	335 km	14 February – 28 August	87 days earlier
Las Vegas	336 km	13 March – 22 August	60 days earlier
Albuquerque	452 km	12 April – 20 July	30 days earlier
Grand Junction	512 km	25 April – 7 July	17 days earlier
Santa Fe (United States)	518 km	27 April – 6 July	15 days earlier

Where to buy tomato plants and seeds near Flagstaff

Buy plants ready to set out from 12 May to 1 July (from 21 April to 1 July for an unheated greenhouse); seed for raising your own is sown from 28 February to 10 May. Within 15 km of Flagstaff OpenStreetMap lists 1 plant nursery and 1 market (collected 28 October 2026).

Sprouts Farmers Market — market
South Riordan Ranch Street 1540, 86001 Flagstaff · Mon–Sun 07:00–22:00 · 4 km · sprouts.com
Viola's Flower Garden — plant nursery
8 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