What is the correct way to plant sweet corn in the home garden?
Sweet corn performs best in fertile, well-drained soils in full sun. Standard sweet corn (su) varieties may be planted in late April in central Iowa. It’s generally recommended that sugar enhanced (se) varieties be planted 1 week later than standard sweet corn varieties. The seeds of shrunken-2 or supersweet (sh2) varieties germinate poorly when soil temperatures are below 65 degrees Fahrenheit. As a result, shrunken-2 varieties should not be planted until mid-May in central Iowa. For a continuous supply of sweet corn, plant early, mid-season, and late varieties or plant every 2 or 3 weeks. The last practical planting date for early varieties is July 1.
Sow seeds at a depth of 1 inch in heavy soils. In light sandy soils, the planting depth may be 2 inches. Space the seeds 8 to 12 inches apart in rows 2½ to 3 feet apart. Sweet corn may also be planted in “hills.” Sow 4 to 5 seeds per hill with approximately 3 inches between seeds. Hills should be spaced 2½ feet apart with 2½ to 3 feet between rows.
Sweet corn is wind pollinated. To insure good pollination and ear development, plant several short rows or blocks rather than 1 or 2 long rows. Inadequate pollination results in poorly filled ears.
Since different types of corn can cross-pollinate and contaminate one another, they should be isolated from each other. All sweet corn types should be isolated from field corn, popcorn, and ornamental corn. Shrunken-2 varieties must also be isolated from sugar-enhanced and standard sweet corn varieties. Cross-pollination between the sh2 and se or su varieties will destroy the quality of both. It is not essential to isolate sugar-enhanced varieties from standard sweet corn.
Isolation can be achieved by planting the different types at least 250 feet from one another and by avoiding prevailing winds. Another method is to stagger planting dates or to select varieties that mature at different times. A minimum of 14 days should separate the tasseling times of the different types.