When to Plant Cucumbers in Colorado
Cool, crisp, and perfect for salads and pickling. Cucumbers thrive in warm weather and produce abundantly.
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 |
Cucumbers 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 Cucumbers in Colorado
Cucumbers in Colorado's Climate
Cucumbers need warmth but mature quickly — 50-60 day varieties fit comfortably within your growing season. Start seeds indoors 3 weeks before last frost and transplant after soil reaches 60°F. Black plastic mulch warms soil for earlier transplanting. Row cover adds warmth during cool June nights. Choose cold-tolerant varieties like Marketmore and pick frequently to keep plants producing.
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 60°F before planting cucumbers 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. Cucumbers 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 cucumbers — transplant timing shifts by several weeks across the state.
Growing Tips
Trellis for straighter fruits and better air circulation. Pick regularly to encourage more production.
Companion Planting
Plant cucumbers alongside these companions for better growth:
Keep cucumbers away from:
The Bottom Line
Last reviewed: March 29, 2026