When to plant sweet corn 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). Sweet Corn needs 60–100 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 sweet corn in Colorado: the short answer
For a spring planting, sow May 7 – May 26. Wait until the soil is at least 55°F and frost is over.
Succession sow again in Colorado: May 26 · Jun 9 · Jun 23 · Jul 7
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 sweet corn in Colorado, step by step
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 24 inches deep, with a pH between 5.8 and 7.0. Dig in compost before planting.
- Sow outdoors (May 7 – May 26). Space plants about 10 inches apart in rows 30 inches apart, sowing seed 1.5 inches deep. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. It needs plenty of water; keep the soil evenly moist and never let it dry out.
- Watch for pests and problems. Pests: corn earworm, European corn borer, corn rootworm, raccoons. Diseases and disorders: common smut, common rust, Stewart's wilt.
- Harvest (from about Jul 11 – Aug 20). Sweet Corn takes 60-100 days to reach harvest. Plant in a block of at least 4 short rows, not one long row, or the ears fill unevenly. Keep sugar-enhanced and supersweet types isolated from field corn. Succeed by sowing every 2 weeks or planting early/mid/late varieties together.
Figures come from our crop data; dates use Colorado’s average frost dates. More in the full sweet corn growing guide.
Sweet Corn 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 sweet corn dates shift with them.
When to plant sweet corn in nearby states
Questions gardeners in Colorado ask
When is the best time to plant sweet corn in Colorado?
Sow sweet corn in Colorado between May 7 and May 26. 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.
What is the latest I can plant sweet corn in Colorado?
About August 2. Sweet corn needs at least 60 days to mature, and frost around October 1 ends the season, so later plantings risk being cut short.
When will sweet corn planted in Colorado be ready to harvest?
Planted on time, sweet corn is usually ready from about July 11 to August 20, 60-100 days after sowing.
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.