When to Plant Broccoli in Illinois
A nutrition powerhouse that thrives in cool weather. Harvest the main head, then enjoy weeks of side shoots.
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 |
Broccoli 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 Broccoli in Illinois
Broccoli in Illinois's Climate
Broccoli grows best in spring and fall in your climate. Fall is the superior season — the gradually cooling temperatures favor tight head formation without the bolting risk of warming spring days. Start fall transplants indoors in late June, set out in late July. After harvesting the main head, leave plants for weeks of side-shoot production.
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.
Illinois Climate & Growing Season
Continental climate with four seasons. Hot, humid summers. Cold winters. Good growing season length in central and southern regions. Broccoli can handle frost well, which is an advantage in Illinois's climate. You can push planting dates earlier in spring and extend into fall.
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 broccoli — but broccoli handle frost well, so the timing difference is less critical.
Growing Tips
Harvest main head while buds are tight. Side shoots will continue producing for weeks after the main harvest.
Companion Planting
Plant broccoli alongside these companions for better growth:
Keep broccoli away from:
The Bottom Line
Last reviewed: March 29, 2026