When to plant lettuce in Colorado
Colorado’s average last spring frost is May 5, and the first fall frost typically arrives around October 1 — about 149 frost-free days (USDA zones 3b, 4b, 5a, 5b, 6a, 7a). Lettuce needs 30–60 days to mature, which fits comfortably within Colorado's growing season.
Colorado covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant lettuce in Colorado: the short answer
For a spring planting, plant out Apr 14 – May 1, with seeds started indoors Mar 31 – Apr 14. Seeds germinate in soil from 35 to 80°F.
Succession sow again in Colorado: May 3 · May 15 · May 27 · Jun 8
Spring succession stops before summer heat makes it bolt. Start sowing again in late summer for a fall crop (see the fall window above).
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow lettuce in Colorado, step by step
- Start seeds indoors (Mar 31 – Apr 14). Sow seeds ⅛ inch deep in seed-starting mix under bright light. They take 2-10 days to sprout, fastest in soil around 65°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. It needs six or more hours of sun for the best growth, though four to six hours in partial shade is enough and loose soil at least 8 inches deep, with a pH between 6.0 and 7.0. Dig in compost before planting.
- Plant out (Apr 14 – May 1). Space plants about 10 inches apart in rows 14 inches apart. It tolerates a light frost but not a hard freeze. As a cool-season crop it does best before summer heat arrives in Colorado.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: aphids, slugs, snails, cutworm. Diseases and disorders: downy mildew, bottom rot, tipburn (calcium disorder).
- Harvest (from about May 21 – Jun 20). Lettuce takes 30-60 days to reach harvest. Seed needs light - barely cover it. Will not germinate above ~80 F soil. Loose-leaf types give the fastest, most forgiving cut-and-come-again harvest.
Figures come from our crop data; dates use Colorado’s average frost dates. More in the full lettuce growing guide.
Lettuce planting dates by USDA zone in Colorado
Colorado spans USDA zones 3b, 4b, 5a, 5b, 6a, 7a. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the lettuce dates shift with them.
| Zone | Last frost | First frost | Season | Start indoors | Plant lettuce |
|---|---|---|---|---|---|
| Zone 3 | May 15 | Sep 15 | 120 days | Apr 10 – Apr 24 | Apr 24 – May 11 |
| Zone 4 | May 10 | Sep 25 | 135 days | Apr 5 – Apr 19 | Apr 19 – May 6 |
| Zone 5 | Apr 30 | Oct 5 | 160 days | Mar 26 – Apr 9 | Apr 9 – Apr 26 |
| Zone 6 | Apr 15 | Oct 15 | 185 days | Mar 11 – Mar 25 | Mar 25 – Apr 11 |
| Zone 7 | Apr 5 | Oct 25 | 200 days | Mar 1 – Mar 15 | Mar 15 – Apr 1 |
When to plant lettuce in nearby states
Questions gardeners in Colorado ask
When is the best time to plant lettuce in Colorado?
Plant lettuce transplants outdoors in Colorado between April 14 and May 1. That timing is set by Colorado's average last spring frost of May 5; Colorado spans several climates, so cooler and higher parts of the state run later.
When should I start lettuce seeds indoors in Colorado?
Start seeds indoors between March 31 and April 14, about 4 weeks before the last frost, so the seedlings are ready to plant out from April 14.
Can I plant lettuce in the fall in Colorado?
Yes. For a fall crop, sow between July 27 and August 13, so the crop matures in cool weather before Colorado's first frost around October 1.
When will lettuce planted in Colorado be ready to harvest?
Planted on time, lettuce is usually ready from about May 21 to June 20, 30-60 days after planting.
When is the last frost in Colorado?
On average around May 5, with the first fall frost around October 1 - about 149 frost-free days. Your town may differ by two weeks or more.