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This article was published originally on 5/24/1996Next to tomatoes, sweet corn is probably the most anticipated vegetable harvested in the garden. Sweet corn differs from field corn because it possesses a recessive sugary (su) gene. Kernels carrying this gene develop nearly twice as much sugar as starchy types. In older sweet corn varieties, the sugar levels are unstable and they change to starch rapidly after harvest. The main interest of sweet corn plant breeders has been the identification of genes that promote high sugar levels and improve post harvest storage properties. Over a dozen genes influencing kernel quality have been identified, but only two are being used extensively. These supersweet corn varieties include the shrunken-2 (sh2) and the sugary enhancer (se) genes.
The sh2 varieties can produce peak sugar levels nearly double that of normal sweet corn. In addition, the conversion of sugar to starch occurs at a much slower rate providing flexibility in harvest and storage. Some varieties will keep 5 to 10 days after harvest. Kernels are very sweet and 'crunchy' (which many people dislike). The newer hybrids have eliminated the skin toughness problem.
These varieties will produce kernels with sugar levels and storage characteristics intermediate between those of normal sweet corn and the best shrunken-2's. The presence of starch contributes to their creamy texture and flavor. The kernels have tender skin, almost too tender for mechanical harvest and extended handling.
Pollination of sweet corn is done by wind. To ensure pollination, plant in short blocks of 3 or 4 rows rather than a single long row. Do not interplant different types of corn or cross-pollination will occur. Dent corn will make sweet corn kernels starchy and less sweet. Popcorn will cross-pollinate with sweet corn unless it is more than 100 feet away. Standard sweet corn varieties will reduce the quality of the supersweets. There are several ways to isolate corn to reduce or eliminate pollination problems. A distance of 700 feet will give complete isolation, however, in most situations this is impractical. A distance of 250 feet will give some contamination, but not enough to materially affect quality. If planting upwind, a distance of 100 to 150 feet is adequate. Isolation can also be provided by time of maturity. There should be a minimum of 14 days between maturities in order to receive isolation. In some cases (cool air and soil temperatures) more than 14 days is necessary between plantings because maturity depends upon the total amount of heat the corn receives. Wait until the first planting is about knee-high before planting the second variety. July 1 would be the latest date for planting early maturing varieties. A final way of isolating corn is through the use of barriers and border rows. A large amount of contaminating pollen can be diluted by using 2 to 5 border rows for protection. Isolation distances can be slightly reduced with these barriers.
Other helpful hints to guarantee sweet corn success:
Year of Publication:
IC-475(13) -- May 24, 1996