When to Plant Sunflowers in Illinois
Few things bring more joy than a row of sunflowers turning their faces to the sun. Easy, dramatic, and pollinator-friendly.
The Short Answer
Illinois Frost Dates
Your planting dates depend on which part of Illinois you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Illinois (Chicago) | 5a, 5b | Apr 25 - May 10 | Oct 1 - Oct 15 |
| Central Illinois | 5b, 6a | Apr 15 - May 1 | Oct 5 - Oct 20 |
| Southern Illinois | 6b, 7a | Apr 1 - Apr 15 | Oct 15 - Nov 1 |
Sunflowers Planting Schedule for Illinois
Northern Illinois (Chicago) (Zones 5a, 5b)
Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15
Central Illinois (Zones 5b, 6a)
Average last frost: Apr 15 - May 1 · Average first frost: Oct 5 - Oct 20
Southern Illinois (Zones 6b, 7a)
Average last frost: Apr 1 - Apr 15 · Average first frost: Oct 15 - Nov 1
Growing Sunflowers in Illinois
Sunflowers in Illinois's Climate
Sunflowers are nearly foolproof in moderate climates. Direct sow after frost and watch them grow a foot or more per week in the summer heat. Succession plant every 2 weeks through late June for blooms all summer. Your reliable warm season gives even the tallest mammoth varieties plenty of time to mature.
Soil Considerations for Illinois
Rich prairie soils — some of the most fertile in the country. Heavy clay in many areas. Well-suited for most vegetables. Make sure soil has warmed to at least 55°F before planting sunflowers outside.
Illinois Climate & Growing Season
Continental climate with four seasons. Hot, humid summers. Cold winters. Good growing season length in central and southern regions. 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 Illinois: Northern Illinois (Chicago) (5a, 5b) has a last frost around Apr 25 - May 10, while Southern Illinois (6b, 7a) sees frost end around Apr 1 - Apr 15. 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