When to plant sweet corn in Iowa
Iowa’s average last spring frost is April 25, and the first fall frost typically arrives around October 8 — about 166 frost-free days (USDA zones 4b, 5a, 5b). Sweet Corn needs 60–100 days to mature, which fits comfortably within Iowa's growing season.
When to plant sweet corn in Iowa: the short answer
For a spring planting, sow Apr 27 – May 16. Wait until the soil is at least 55°F and frost is over.
Succession sow again in Iowa: May 16 · May 30 · Jun 13 · Jun 27 · Jul 11 · Jul 25
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 Iowa, 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 (Apr 27 – May 16). 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 1 – Aug 10). 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 Iowa’s average frost dates. More in the full sweet corn growing guide.
Sweet Corn planting dates by USDA zone in Iowa
Iowa spans USDA zones 4b, 5a, 5b. 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 Iowa ask
When is the best time to plant sweet corn in Iowa?
Sow sweet corn in Iowa between April 27 and May 16. That timing is set by Iowa's average last spring frost of April 25.
What is the latest I can plant sweet corn in Iowa?
About August 9. Sweet corn needs at least 60 days to mature, and frost around October 8 ends the season, so later plantings risk being cut short.
When will sweet corn planted in Iowa be ready to harvest?
Planted on time, sweet corn is usually ready from about July 1 to August 10, 60-100 days after sowing.
When is the last frost in Iowa?
On average around April 25, with the first fall frost around October 8 - about 166 frost-free days. Your town may differ by two weeks or more.