When to Plant Zinnias in Minnesota
The cut-and-come-again champion. The more you cut zinnias, the more they bloom. A cottage garden essential.
The Short Answer
Minnesota Frost Dates
Your planting dates depend on which part of Minnesota you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Minnesota | 3a, 3b | May 15 - Jun 1 | Sep 5 - Sep 20 |
| Central Minnesota | 3b, 4a | May 5 - May 20 | Sep 15 - Oct 1 |
| Southern Minnesota | 4a, 4b | Apr 25 - May 10 | Sep 25 - Oct 10 |
Zinnias Planting Schedule for Minnesota
Northern Minnesota (Zones 3a, 3b)
Average last frost: May 15 - Jun 1 · Average first frost: Sep 5 - Sep 20
Central Minnesota (Zones 3b, 4a)
Average last frost: May 5 - May 20 · Average first frost: Sep 15 - Oct 1
Southern Minnesota (Zones 4a, 4b)
Average last frost: Apr 25 - May 10 · Average first frost: Sep 25 - Oct 10
Growing Zinnias in Minnesota
Zinnias in Minnesota's Climate
Zinnias are one of the best annual cut flowers for cold climates — they grow fast enough to bloom for months even in short seasons. Direct sow after your last frost when soil reaches 60°F. The more you cut, the more they bloom, producing armloads of color from July through first hard frost.
Soil Considerations for Minnesota
Rich prairie soils in south and west. Rocky and thin soils in north. Generally excellent for gardening in southern half. Make sure soil has warmed to at least 60°F before planting zinnias outside.
Minnesota Climate & Growing Season
Long, cold winters. Warm summers. Short but productive growing season with long summer days. Hardy varieties essential. Zinnias 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 Minnesota: Northern Minnesota (3a, 3b) has a last frost around May 15 - Jun 1, while Southern Minnesota (4a, 4b) sees frost end around Apr 25 - May 10. This difference matters for zinnias — transplant timing shifts by several weeks across the state.
Growing Tips
Water at the base to prevent powdery mildew. Cut flowers just above a leaf node to encourage more branching and blooms.
Companion Planting
Plant zinnias alongside these companions for better growth:
The Bottom Line
Last reviewed: March 29, 2026