Plant between May 15th and June 10th. If the soil is not warm enough, seeds often rot before sprouting - especially when not treated with fungicide. Untreated corn seeds should be planted only when the soil has warmed up above 18°C (65°F) - warmer for supersweet (sh2) types, and even warmer for a good stand. Use a soil thermometer. If spring weather is cold, consider planting in flats indoors with bottom heat for transplanting. Seeds should germinate in 7-10 days. If it rains after planting and corn does not emerge, just replant the area.