When to Plant Broccoli in Colorado
A nutrition powerhouse that thrives in cool weather. Harvest the main head, then enjoy weeks of side shoots.
The Short Answer
Colorado Frost Dates
Your planting dates depend on which part of Colorado you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Front Range (Denver) | 5a, 5b, 6a | May 1 - May 15 | Sep 25 - Oct 10 |
| Western Slope | 4b, 5a, 5b, 6a | May 10 - Jun 1 | Sep 15 - Oct 5 |
| Mountain Regions | 3a, 3b, 4a, 4b | Jun 1 - Jun 20 | Aug 25 - Sep 15 |
Broccoli Planting Schedule for Colorado
Front Range (Denver) (Zones 5a, 5b, 6a)
Average last frost: May 1 - May 15 · Average first frost: Sep 25 - Oct 10
Western Slope (Zones 4b, 5a, 5b, 6a)
Average last frost: May 10 - Jun 1 · Average first frost: Sep 15 - Oct 5
Mountain Regions (Zones 3a, 3b, 4a, 4b)
Average last frost: Jun 1 - Jun 20 · Average first frost: Aug 25 - Sep 15
Growing Broccoli in Colorado
Broccoli in Colorado's Climate
Broccoli thrives in your cool climate. Spring planting works well — transplant 2-3 weeks before last frost. Unlike warmer regions where heat causes premature bolting, your moderate summer temperatures often allow extended broccoli harvests. Fall broccoli is equally productive. Northern Michigan, Minnesota, and Wisconsin can even grow broccoli through summer in cooler years.
Soil Considerations for Colorado
Alkaline clay soils common along Front Range. Rocky, thin soils in mountains. Amend heavily with compost and sulfur to lower pH.
Colorado Climate & Growing Season
High altitude means intense sun but cool nights. Low humidity. Hail risk in late spring. Short but intense growing season at elevation. Broccoli can handle frost well, which is an advantage in Colorado's climate. You can push planting dates earlier in spring and extend into fall.
Growing season length varies across Colorado: Front Range (Denver) (5a, 5b, 6a) has a last frost around May 1 - May 15, while Mountain Regions (3a, 3b, 4a, 4b) sees frost end around Jun 1 - Jun 20. 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