Linda Geist
Sweet cornYour Show-Me Garden: MU Extension brings you gardening tips from experts around the state.

COLUMBIA, Mo. – Nothing says summer like steaming hot, homegrown sweet corn dripping with butter.

University of Missouri Extension horticulturist David Trinklein says that when he was growing up, his family took great pride in having sweet corn ready by July 4. “Failure to do so would be a source of public embarrassment,” he said.

Properly preparing sweet corn involves the following ritual. First, bring a pot of water to a slow boil. Send a family member to the corn patch. The family member should be someone schooled in the art of knowing when sweet corn is at its best. They will know how to pick only perfectly developed ears—not too juicy, not too chewy. They will silk the ears as they walk briskly back to the house. Lower corncobs gently into boiling water. Cook three to five minutes. Remove from the water. Slather with butter and salt to taste.

Trinklein says there is a method to the madness of the sweet corn ritual. Sweet corn begins to convert sugar to starch the moment it is picked. Sweetness drops each minute between harvest and consumption. Haste makes taste, if you will. That’s why farmers market vendors pride themselves on offering “picked fresh this morning” corn.

Sweet corn is a mutant strain of corn with twice the sugar content of field corn. Today there are more than 200 varieties available to the gardening public.

Over the years, scientists have made sweet corn even sweeter. Varieties also have been developed to improve the shelf life of the sweet taste.

First, there were the so-called “supersweet” varieties that contain about three times as much sugar as regular sweet corn. Supersweet types, however, don’t germinate well in cool soils and bear kernels that are on the chewy side. Some people find them too sweet. Illini Xtra Sweet and Providence are two popular supersweet varieties.

Supersweet varieties were followed by sugar-enhanced (SE) or Everlasting Heritage varieties. These varieties start about two times sweeter than normal sweet corn and stay sweeter longer after being harvested. Ambrosia, Bodacious, Delectable, Gold Nuggets, Incredible and Silver King are popular SE varieties.

Synergistic hybrids boast high yields, good vigor, delectable sweetness, disease tolerance and good holding quality. In essence, Trinklein says, they combine the best traits of supersweet and sugar-enhanced types into one variety. Synergistic hybrids include popular varieties such as Applause, Cameo, Honey Select, Pay Dirt, Providence and Silver Duchess.

Sweet corn is a warm-season crop that needs at least eight hours of direct sun to thrive. Avoid planting new sweeter varieties until ground temperature reaches at least 60 degrees. Use the frost-free date as the benchmark for older varieties.

Plant seeds about 1 inch deep and 8-10 inches apart. Space rows 30-42 inches apart. Sweet corn is wind-pollinated, so plant in blocks rather than a single straight line, says Trinklein.

Avoid cross-pollination of supersweet and other varieties by staggering planting dates by 14 days or planting at least 250 feet apart.

Sweet corn is a heavy feeder and requires a balanced pre-plant fertilizer such as 10-10-10 at the rate of 2-3 pounds per 100 square feet. Side-dress plants with additional nitrogen at tasseling. Water well, especially when the kernels fill as the silks begin to dry.

Few diseases plague sweet corn, but insects (and raccoons) do. Corn earworms, cutworms, armyworms, wireworms and rootworms damage corn. Proper garden cleanup in the fall helps avoid insect infestation. Also, avoid planting sweet corn in ground that was not clean-tilled the previous year. Corn earworm is the most problematic insect pest of sweet corn but can be controlled by timely applications of carbaryl (Sevin).

Sweet corn usually matures 22-24 days after silking. Silks turn brown and tips of the ears become blunt when corn is at the edible stage. Test readiness of corn by slightly pulling back the husk and silk. Kernels should fill the ear completely. Puncture a kernel using a fingernail. Liquid from the kernel will be watery if the corn is not ready to harvest. If it is past prime, it will be creamy or doughy. Milky liquid indicates readiness.

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