When to plant zucchini in Helena: 3 July – 17 July

In Helena, zucchini: sow for seedlings from 22 May to 26 June; plant into a greenhouse from 12 June to 17 July; plant out into open ground from 3 July to 17 July. For plants and seeds, the places nearby include Keeping It Green (plant nursery, 1 km); addresses and opening hours are below.

Zucchini 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 zucchini 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 36 days to the first harvest leave 56 for picking, so a start 8 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
First autumn frost	3 October, 92 days after the start
Days in the bed to the first harvest (card)	36
First harvest, if planted in this window	8 August – 22 August
Days left for picking	56
Daylight	15:47 on 12 June, 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, Eggplant, Pumpkin and Watermelon.

Zucchini in Helena: care after planting

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

Pests and diseases of zucchini to watch for:

Weather in Helena during the zucchini season

About 137 mm of rain falls in the season; July is the driest month (23 mm) and October the wettest (46 mm).

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

Zucchini in nearby cities

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

City	Distance	Date	Difference
Missoula	155 km	30 June – 20 July	3 days earlier
Billings	287 km	2 June – 28 July	31 days earlier
Idaho Falls	345 km	4 June – 28 July	29 days earlier
Spokane	425 km	22 May – 29 July	42 days earlier
Boise	466 km	7 May – 10 August	57 days earlier
Calgary	517 km	18 June – 15 July	15 days earlier

Where to buy zucchini plants and seeds near Helena

Buy plants ready to set out from 3 July to 17 July (from 12 June to 17 July for an unheated greenhouse); seed for raising your own is sown from 22 May to 26 June. Within 15 km of Helena OpenStreetMap lists 2 farm-supply shops and 6 plant nurseries (collected 28 October 2026).

Keeping It Green — plant nursery
Columbia Avenue 2005, 59601 Helena · 1 km · keeping-it-green-helena.com
Gardenwerks: Nursery & Landscaping — plant nursery
2 km
Chadwick Nursery — plant nursery
4 km
Valley Farms — plant nursery
5 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