Cool-Season Vegetable

When to Plant Cauliflower in Colorado

The diva of the brassica family. More temperamental than broccoli but worth the extra attention.

The Short Answer

Cauliflower are cold-tolerant and do well in Colorado's humid climate. Colorado gardeners can also plant a fall crop. Alkaline clay soils common along Front Range. Rocky, thin soils in mountains. Amend heavily with...

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

Cauliflower 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

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks before frost
Fall Planting
10 wks before first frost

Western Slope (Zones 4b, 5a, 5b, 6a)

Average last frost: May 10 - Jun 1 · Average first frost: Sep 15 - Oct 5

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks before frost
Fall Planting
10 wks before first frost

Mountain Regions (Zones 3a, 3b, 4a, 4b)

Average last frost: Jun 1 - Jun 20 · Average first frost: Aug 25 - Sep 15

Start Seeds Indoors
6 wks before frost
Transplant Outside
2 wks before frost
Fall Planting
10 wks before first frost

Growing Cauliflower in Colorado

Cauliflower in Colorado's Climate

Cauliflower is more demanding than broccoli — it needs steady 60-70°F temperatures during heading, which your unpredictable spring weather may not provide. Fall is the better season: start indoors in mid-June, transplant in mid-July, and let the gradual autumn cool-down produce tight, clean heads. Temperature swings cause buttoning (premature tiny heads).

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.

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 cauliflower — adjust your planting dates to match your specific region.

Growing Tips

Blanch white varieties by tying outer leaves over the head when it reaches 2 inches. Temperature swings cause buttoning.

Companion Planting

Plant cauliflower alongside these companions for better growth:

Beets Celery Onions

Keep cauliflower away from:

Strawberries Tomatoes

The Bottom Line

Cauliflower can be grown successfully across Colorado, but your exact planting dates depend on which region you're in. Front Range (Denver) gardeners should plan around a May 1 - May 15 last frost, while those in Mountain Regions can typically plant later. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Cauliflower Growing Guide National planting guide with all states Colorado Planting Calendar All plants for Colorado Cauliflower in Alabama Alabama planting dates Cauliflower in Alaska Alaska planting dates Cauliflower in Arizona Arizona planting dates Cauliflower in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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