Warm-Season Vegetable

When to Plant Corn (Sweet) in Iowa

Nothing says summer like fresh sweet corn. Plant in blocks (not rows) for proper pollination.

The Short Answer

In Iowa, corn (sweet) planting dates vary by region. In Northern Iowa, your average last frost is around May 5 - May 20, while Southern Iowa sees its last frost around Apr 20 - May 5. Since corn (sweet) are frost-sensitive, direct sow 2 weeks after your last frost date. Outstanding black prairie soils. Some of the richest agricultural land in the world. Minimal amendment needed.

Iowa Frost Dates

Your planting dates depend on which part of Iowa you're in. Here are the frost date ranges by region:

Region Zones Last Frost (Spring) First Frost (Fall)
Northern Iowa 4b, 5a May 5 - May 20 Sep 20 - Oct 5
Central Iowa 5a, 5b Apr 25 - May 10 Oct 1 - Oct 15
Southern Iowa 5b Apr 20 - May 5 Oct 5 - Oct 20

Corn (Sweet) Planting Schedule for Iowa

Northern Iowa (Zones 4b, 5a)

Average last frost: May 5 - May 20 · Average first frost: Sep 20 - Oct 5

Direct Sow
2 wks after frost

Central Iowa (Zones 5a, 5b)

Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15

Direct Sow
2 wks after frost

Southern Iowa (Zones 5b)

Average last frost: Apr 20 - May 5 · Average first frost: Oct 5 - Oct 20

Direct Sow
2 wks after frost

Growing Corn (Sweet) in Iowa

Corn (Sweet) in Iowa's Climate

Sweet corn needs warm soil and warm nights but matures quickly enough for most cold-climate gardens. Direct sow when soil reaches 60°F — typically late May. Choose early varieties (60-65 days) for the shortest seasons. Plant in blocks of at least 4×4 for wind pollination. Raccoons are the universal corn nemesis — electric fencing is the only reliable deterrent.

Soil Considerations for Iowa

Outstanding black prairie soils. Some of the richest agricultural land in the world. Minimal amendment needed. Make sure soil has warmed to at least 60°F before planting corn (sweet) outside.

Iowa Climate & Growing Season

Continental climate. Cold winters, warm humid summers. Good growing season with adequate rainfall. Corn (Sweet) 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 Iowa: Northern Iowa (4b, 5a) has a last frost around May 5 - May 20, while Southern Iowa (5b) sees frost end around Apr 20 - May 5. This difference matters for corn (sweet) — transplant timing shifts by several weeks across the state.

Growing Tips

Plant in blocks of at least 4x4 for wind pollination. Corn is a heavy feeder — amend soil with compost before planting.

Companion Planting

Plant corn (sweet) alongside these companions for better growth:

Beans Squash Melons

Keep corn (sweet) away from:

Tomatoes

The Bottom Line

Corn (Sweet) can be grown successfully across Iowa, but your exact planting dates depend on which region you're in. Northern Iowa gardeners should plan around a May 5 - May 20 last frost, while those in Southern Iowa can typically plant earlier. For exact dates based on your zip code, use our free planting date finder.

Related Guides

Corn (Sweet) Growing Guide National planting guide with all states Iowa Planting Calendar All plants for Iowa Corn (Sweet) in Alabama Alabama planting dates Corn (Sweet) in Alaska Alaska planting dates Corn (Sweet) in Arizona Arizona planting dates Corn (Sweet) in Arkansas Arkansas planting dates
Note: All dates are based on NOAA 30-year Climate Normals and represent historical averages, not predictions for any specific year. Always check your local weather forecast before planting frost-sensitive crops. Learn about our data sources.

Last reviewed: March 29, 2026

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