Plant seeds directly in the garden in the spring after the danger of frost has passed, roughly 1-2 weeks after the average last frost date. Corn requires warm soil and air conditions during much of the growing season to produce a quality crop. Optimum soil temperature for seed germination is 65-85 degrees. Corn is wind pollinated and should be planted in blocks or 3-4 rows side by side to ensure good pollination. Make successive planting for continuous harvest all summer. Plan for the last planting to mature a few weeks before the average first frost date. Because different corn varieties cross-pollinate you must isolate your sweet corn from field corn, popcorn, and ornamental corn. Failure to do so will result in cross-pollination and kernels that taste starchy rather than sweet. You can isolate corn in space or in time. To isolate in space, separate varieties by at least 250 feet, preferably 400-500 feet. Try not to plant one variety downwind from another. To isolate in time, plant so maturity date for each variety is separated by at least 14 days. When you do this, pollen of one variety is released before the silks of the other variety are produced and cross-pollination does not occur.
