When to Plant Lettuce in Colorado
Fast-growing and forgiving. Plant in spring and fall for a nearly year-round supply of fresh salad greens.
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 |
Lettuce 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 Lettuce in Colorado
Lettuce in Colorado's Climate
Your cool climate is actually excellent for lettuce — the crop thrives in 55-70°F conditions that you have for months. Direct sow as soon as soil thaws in spring and continue harvesting well into summer because your moderate temperatures delay bolting far longer than in southern states. Fall lettuce is equally productive. In the coldest zones, cold frames extend harvest into December.
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 lettuce — adjust your planting dates to match your specific region.
Growing Tips
Succession plant every 2-3 weeks for continuous harvest. Shade cloth extends the season into warmer months.
Companion Planting
Plant lettuce alongside these companions for better growth:
The Bottom Line
Last reviewed: March 29, 2026