When to Plant Pumpkins in Colorado
From jack-o-lanterns to pies, pumpkins need space and time but deliver a uniquely satisfying harvest.
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 |
Pumpkins 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 Pumpkins in Colorado
Pumpkins in Colorado's Climate
Pumpkin growing is a calendar countdown — count backward from your target harvest date (usually mid-October for Halloween) using your variety's days-to-maturity. In short-season zones, choose 90-day varieties and start seeds indoors 3 weeks before last frost. Black plastic mulch warms soil for earlier transplanting. Squash vine borer is less common in cold zones — a genuine advantage.
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. Make sure soil has warmed to at least 65°F before planting pumpkins outside.
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. Pumpkins 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 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 pumpkins — transplant timing shifts by several weeks across the state.
Growing Tips
Count backwards from when you want ripe pumpkins (usually October). They need 90-120 days, so mid-June to early July is often ideal.
Companion Planting
Plant pumpkins alongside these companions for better growth:
Keep pumpkins away from:
The Bottom Line
Last reviewed: March 29, 2026