When to Plant Basil in Montana
The king of herbs. Basil and tomatoes are best friends in the garden and in the kitchen.
The Short Answer
Montana Frost Dates
Your planting dates depend on which part of Montana you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Western Montana | 4b, 5a, 5b | May 10 - May 30 | Sep 10 - Sep 30 |
| Central Montana | 3b, 4a, 4b | May 15 - Jun 5 | Sep 5 - Sep 20 |
| Eastern Montana | 3a, 3b, 4a | May 10 - Jun 1 | Sep 10 - Sep 25 |
Basil Planting Schedule for Montana
Western Montana (Zones 4b, 5a, 5b)
Average last frost: May 10 - May 30 · Average first frost: Sep 10 - Sep 30
Central Montana (Zones 3b, 4a, 4b)
Average last frost: May 15 - Jun 5 · Average first frost: Sep 5 - Sep 20
Eastern Montana (Zones 3a, 3b, 4a)
Average last frost: May 10 - Jun 1 · Average first frost: Sep 10 - Sep 25
Growing Basil in Montana
Basil in Montana's Climate
Basil needs warmth and dies at the first hint of frost. Start seeds indoors 6 weeks before your last frost and don't transplant until nights stay above 55°F — often 2-3 weeks after your official last frost date. Your growing window may be only 10-14 weeks, so make them count: pinch flower buds aggressively and harvest often. Consider growing in containers you can move indoors during unexpected cold snaps.
Soil Considerations for Montana
Alkaline soils common. Thin, dry soils in east. Better soils in valleys. Wind erosion challenges. Make sure soil has warmed to at least 60°F before planting basil outside.
Montana Climate & Growing Season
Short, intense growing season. Low humidity. Wide day-night temperature swings. Wind protection valuable. Basil cannot tolerate any frost, so wait until all frost danger has passed before transplanting outside. Watch local forecasts carefully in spring.
Growing season length varies across Montana: Western Montana (4b, 5a, 5b) has a last frost around May 10 - May 30, while Eastern Montana (3a, 3b, 4a) sees frost end around May 10 - Jun 1. This difference matters for basil — transplant timing shifts by several weeks across the state.
Growing Tips
Pinch off flower buds to keep leaves producing. Harvest from the top down, cutting just above a leaf pair. Succession plant for season-long supply.
Companion Planting
Plant basil alongside these companions for better growth:
Keep basil away from:
The Bottom Line
Last reviewed: March 29, 2026