Sweet corn is the most popular variety of home garden grown corn, due to its flavor advantage over varieties of field corn. The better taste of sweet corn is due to its high sugar content - sweet corn contains up to 12% sugar, twice the amount found in field corn!
Sweet corn was initially developed by the Asgrow Seed Company in the 1920's, the company producing the first hybrids of the variety. However, sweet corn is at a disadvantage in that it doesn't keep very well; within twenty-four hours of the time it is picked, most of the sugar in the kernels has turned to starch. Breeders have been trying to develop a hybrid that tastes sweeter and keeps better.
Also in development are the new sugary corns, classified as "supersweet" corn; a variety which contains up to thirty percent sugar. This is advantageous in that the sugar doesn't change to starchy carbohydrates quite as fast. "Sugar-Enhanced" varieties boast a sweetness that may be cM classified somewhere between the two, and are able to hold their sweet flavor longer than traditional sweet corn.
Cross-pollination is a major consideration in the growth of sweet corn. Isolation of the plants is often necessary to avoid contamination. A distance of 700 feet will give complete isolation, but is used only for scientific and plant breeding purposes. A separation of 250 feet will result in some contamination, but not enough to materially affect the quality of the crop. Wind direction has a direct affect - isolation may be enhanced by positioning the corn to avoid prevailing winds. Barriers and border rows provide the plants with protection. A considerable amount of contaminating pollen can be diluted by using two to five border rows for protection. Using these rows, the 250 foot separation distance can be reduced. Isolation may be provided by the time the crops reach maturity. There should be a 14-day minimum difference between maturities of the different varieties. With this in mind, schedule varieties and planting times accordingly.
Following are examples of sweet corn available:
Normal Sweet: Gold Cup, Silver Queen. Super Sweets: Early Extra Sweet, Illinois Extra Sweet. Synergistic or sugary super sweets: Sugar Loaf, Honeycomb. Gene Combination (ADX): Pennfresh ADX Modified Sugary (EH): Kandy Korn EH, Mainliner EH, Golden Sweet EH, and other EH types. The sweet corn types Super Sweet (2) and ADX (4) must be isolated from all other types of sweet corn and from each other. Pollen from other types will make their kernels starchy and no different from field corn. If a Super Sweet pollinates ADX or vice versa, the kernels will be starchy. Also, pollen from Super Sweet or ADX will turn normal sweet corn (1) starchy. Both types (3) and (5) will have normal sweetness when pollinated by normal sweet corn (1). The pollen from types (3) and (5) do not affect normal sweet corn (1). One or two rows of (3) or (5) in a large field will not allow full expression of their sweetness because they will be diluted by the normal sweet corn pollen. Plant single rows for trial on the west outside section of the field.
Ohio State University Commercial Growers' Vegetable and Potato News : April 11, 1980. (Edited for Hortopics: 5/80, by B. Zandstra).
The Great Lakes Vegetable Grower's News Volume 20, Number 9 September 1986 "Sweet, Sweeter and Supersweet corn"