When to Plant Marigolds in Illinois
The ultimate companion plant. Marigolds repel pests, attract pollinators, and add cheerful color all season long.
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 |
Marigolds 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 Marigolds in Illinois
Marigolds in Illinois's Climate
Marigolds are a garden essential in moderate climates — both beautiful and functional. Transplant after last frost and enjoy blooms until hard freeze. Plant French marigolds throughout your vegetable garden for broad pest deterrence. Deadhead for continuous bloom.
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 60°F before planting marigolds outside.
Illinois Climate & Growing Season
Continental climate with four seasons. Hot, humid summers. Cold winters. Good growing season length in central and southern regions. Marigolds 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 marigolds — transplant timing shifts by several weeks across the state.
Growing Tips
French marigolds are best for pest control in vegetable gardens. Deadhead spent flowers to keep them blooming until frost.
Companion Planting
Plant marigolds alongside these companions for better growth:
The Bottom Line
Last reviewed: March 29, 2026