When to Plant Sunflowers in Montana
Few things bring more joy than a row of sunflowers turning their faces to the sun. Easy, dramatic, and pollinator-friendly.
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 |
Sunflowers 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 Sunflowers in Montana
Sunflowers in Montana's Climate
Sunflowers are surprisingly well-suited to cold climates — they grow fast enough to bloom before frost even in zones with 100-day seasons. Direct sow 1-2 weeks after your last frost. The intense summer daylight in northern latitudes actually produces taller stalks and larger heads. Choose varieties under 90 days to maturity for the shortest-season areas.
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 55°F before planting sunflowers outside.
Montana Climate & Growing Season
Short, intense growing season. Low humidity. Wide day-night temperature swings. Wind protection valuable. Sunflowers 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 sunflowers — transplant timing shifts by several weeks across the state.
Growing Tips
Direct sow is preferred — sunflowers don't love transplanting. Succession plant every 2 weeks for blooms all summer.
Companion Planting
Plant sunflowers alongside these companions for better growth:
Keep sunflowers away from:
The Bottom Line
Last reviewed: March 29, 2026