When to plant eggplants in Helena: 3 July – 25 July

In Helena, eggplant: sow for seedlings from 13 April to 26 May; plant into a greenhouse from 12 June to 25 July; plant out into open ground from 3 July to 25 July.

Eggplant in Helena: soil, season and weather

In Helena the soil, not frost, sets the date: the last frost is over around 19 May, but the top 7 cm of soil reaches 18 °C — the minimum on the eggplant card — only around 3 July, 45 days later. 92 days separate planting out (3 July) from the first autumn frost (3 October); the card's 70 days to the first harvest leave 22 for picking, so a start 3 weeks late would still fit.

Last spring frost	19 May
Top 7 cm of soil at 18 °C	3 July, 45 days after the last frost
Into an unheated greenhouse	12 June – 25 July; June outside: 7.9 °C at night, 21.8 °C by day; card 21–29 °C
First autumn frost	3 October, 92 days after the start
Days in the bed to the first harvest (card)	70
First harvest, if planted in this window	11 September – 3 October
Days left for picking	22
Daylight	14:31 on 4 May, 15:45 on 3 July
Watering outdoors when fruiting (card)	every 3 days; the driest month, July, has 6 rainy days

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

Eggplant in Helena: care after planting

Planted on 3 July: in the first weeks water every 4 days.

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

3 July — feed: balanced (NPK)
31 July — feed: nitrogen

Pests and diseases of eggplant 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 Helena during the eggplant season

No month of the season averages above the eggplant card's 21–29 °C by day; the warmest, July, averages 27.3 °C. Months that stay below 21 °C even by day on average: October (12 °C). Nights average below 21 °C in every month of the season, from 0.6 °C to 12.1 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
July	27.3	12.1	23	6	15:29
August	26.5	11.5	28	5	14:14
September	21.1	7.4	40	7	12:36
October	12	0.6	46	9	10:58

ERA5 2016–2025, Open-Meteo

Eggplant in nearby cities

All the nearest cities on our list plant eggplant earlier than Helena; the closest date is in Missoula, 3 days earlier.

City	Distance	Date	Difference
Missoula	155 km	30 June – 28 July	3 days earlier
Billings	287 km	2 June – 24 June	31 days earlier
Idaho Falls	345 km	4 June – 24 June	29 days earlier
Spokane	425 km	22 May – 25 June	42 days earlier
Boise	466 km	7 May – 7 July	57 days earlier
Calgary	517 km	18 June – 23 July	15 days earlier

Where to buy eggplant plants and seeds near Helena

Buy plants ready to set out from 3 July to 25 July (from 12 June to 25 July for an unheated greenhouse); seed for raising your own is sown from 13 April to 26 May. Within 15 km of Helena OpenStreetMap lists 2 farm-supply shops and 6 plant nurseries (collected 28 October 2026).

Montana Nursery & Landscape Supply — plant nursery
7 km
Korpi Lawn and Landscape — plant nursery
7 km
Helena Farm Supply — farm supply
9 km
Agri Feeds & Fertilizer — farm supply
3 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